First published on July 23, 2001.

• When you gotta do it, you'll do it. For your mind won't find peace until a goal is reached. I presented earlier this month of July 2001 an **algorithm to calculate the index, or rank, or lexicographical order, or combination sequence number (CSN)**. The algorithm was 100% precise. It had one problem, however. The speed of execution left much to be desired for monster-odds games, such as Keno (80/20, 70/20, even 70/10). The speed was acceptable for many other lotto games. Even a big game such as the 49/5/42 PowerBall required less than half a minute to determine the CSN. Nevertheless, running the algorithm for Keno games took an eternity!

I came back to the original **B. P. Buckles and M. Lybanon** algorithm (**algorithm ACM #515**). I was able to add to it the reverse task: Calculate the CSN for any lotto game, but the Powerball. Later, the PowerBall was added to the procedure, plus a function for Euromillions.

I recompiled **NTHINDEX** to **SEQUENCE**, the program that uses the new algorithm. All my lexicographical order software is freeware at the software download site (but only for registered members).

There you have the two main algorithms for the combinatorics tasks of lexicographic ordering. Listed is also my function that calculates the number of combinations *N taken M at a time*: Combine## (N, M).

Here is the very first lexicographic order algorithm for the sets known as combinations (e.g. lotto drawings). The lexicographic order algorithm was developed by * B. P. Buckles and M. Lybanon* to

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' *** the first combination lexicographic order algorithm by B. P. Buckles and M. Lybanon ' converted from FORTRAN to BASIC ' V = the biggest number in the lotto game (e.g. 49, or 80, etc.) ' K = numbers per combination (e.g. 6, 10, 20, etc.) ' L = lexicographical index to find a combination (e.g. the 1st, the last, 100005th, etc.) REDIM C(K) LI## = 0 P1 = K - 1 FOR I = 1 TO P1 C(I) = 0 IF I <> 1 THEN C(I) = C(I - 1) END IF 1101 C(I) = C(I) + 1 R1 = Combine(V - C(I), K - I) 'call the combination calculator LI = LI + R1 IF LI < L THEN GOTO 1101 END IF LI = LI - R1 NEXT I C(K) = C(P1) + L – LI ' building the array (the sought combination)

In 2001 I discovered the opposite algorithm: **Calculate the index (lexicographical order) when the combination is given.**

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' *** the new 'combination index (rank)' algorithm by Ion Saliu ' V = the biggest number in the lotto game (e.g. 49, or 80, etc.) ' K = numbers per combination (e.g. 6, 10, 20, etc.) REDIM C(K) REDIM Num(K) 'the numbers in the combination LI## = 0 CSN## = 0 P1 = K - 1 FOR I = 1 TO P1 C(I) = 0 If I <> 1 THEN C(I) = C(I - 1) 2001 C(I) = C(I) + 1 R## = Combine(V - C(I), K - I) 'call the combination calculator LI## = LI## + R## IF C(I) < Num(I) THEN GOTO 2001 ' the key command by Ion Saliu LI## = LI## - R## NEXT I CSN## = LI## + Num(K) - Num(P1) 'combination sequence number --- FUNCTION Combine(N AS LONG, M AS LONG) AS EXT DIM iC AS LONG DIM jC AS LONG DIM FA AS EXT DIM va AS EXT REM *** This function calculates the total number of combinations *** REM *** 'N taken M at a time' FA = 1 FOR iC = 1 TO M: FA = FA * iC: NEXT iC va = 1 FOR jC = (N - M + 1) TO N: va = va * jC: NEXT jC Combine = va / FA END FUNCTION

Calculating total number of combinations is as easy as calling the Combination function. For example, a lotto 6 from 49 game:

v = 49

k = 6

**TotalCombinations = Combine(v, k)
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- Download
**LexicographicAlgorithms**

**Download****LexicographicAlgorithms.bas**, the source code.

~ *FindCombo*, the function that finds the combination for a given index (the original algorithm by B. P. Buckles and M. Lybanon);

~ *FindIndex*, the function that finds the index for a given combination (Ion Saliu's lexicographic algorithm).

Downloading requires Permanent Membership. Please read first: * Terms of Service: Paid Membership Required to Download Free Software, Source Code*.

Read Ion Saliu's first book in print: *Probability Theory, Live!*

~ Founded on valuable mathematical discoveries with a wide range of scientific applications, including the organic connection between probability theory and sets of numbers — permutations, combinations, arrangements, lexicographical order.

This is a comprehensive list of my writings on the topic of *lexicographical order* or *indexing*, including algorithms and software.

of permutations, exponential sets, combinations.**Lexicographic, lexicographical order, index, rank**

**This is the most intuitive, if not the best, introduction to the apparently difficult concept of lexicographic ordering of all types of numeric sets.**.**Lexicographical Order: Lotto, Powerball, Mega Millions, Euromillions**

This is the most comprehensive and intuitive presentation of the concept of lexicographic ordering (or indexing), including the superior software to tackle the task.: The Comprehensive and Fast Algorithm.**Combination Lexicographic Order, Rank, Index**

I expanded the lexicographical index concept to two-in-one games, particularly the U.S. lotto game of Powerball (applicable to Mega Millions as well).of lotto data files.**Calculate the combination lexicographic order**

The introduction of**DrawIndex**, the software that calculates the lexicographic indexes for every combination (draw) in a lotto results file.-
The following are older and somehow outdated materials I wrote on lexicographical order subjects. Most of the older software is outdated. Nothing (in the whole world) can beat
.**Index, rank lexicographic order lotto combination**.**Software combination algorithm formula index ordering**Debates.**Combination sequence number or Lexicographic Order****LexicographicOrderAlgorithms.zip**(Lexicographic Order Algorithms).

**LexicographicSets**or**DrawIndex**. Sentimentalism is good only to a close extent.

Of course, everybody loves to feast on great software, especially when it is free! My combinatorics software (and other categories) is absolutely free to run, for an unlimited period of time. However, only the registered members have a right to download the software. Membership requires a nominal fee — the most reasonable there is to connect to the greatest and most useful software ever created. No kidding! Read the conditions to becoming a registered member: * Download Great Free Software: Paid Membership Required*.

- Download the
**software**from the software download site:

**LexicographicSets**, the universal permutations, arrangements and combinations lexicographic indexing (ranking);

**DrawIndex**- highly automated lexicographical indexing for lotto draw files.

**NthIndex**~ lexicographic indexing superseded by LexicographicSets;

**SEQUENCE**~ lexicographic indexing superseded by LexicographicSets;

**COLORDER**- lexicographical indexing for lotto and Powerball only;

**PermuteCombine**, the universal permutations, arrangements and combinations generator for any numbers and words;

**Combinations**, the universal combinations generator for any lotto, Keno, Powerball game: N numbers taken M at a time, in K steps;

**WRITER**, random generator of letters to words, passwords, sentences.