cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A019312 Taxman sequence: define T(S) by max{x+T(S \ {c : c|x})}, where the max is over all x in S for which S also contains a proper divisor of x; if no such x exists, T(S)=0; set T(n)=T({1,...,n}).

Original entry on oeis.org

0, 2, 3, 7, 9, 15, 17, 21, 30, 40, 44, 50, 52, 66, 81, 89, 93, 111, 113, 124, 144, 166, 170, 182, 198, 224, 251, 279, 285, 301, 303, 319, 352, 386, 418, 442, 448, 486, 503, 525, 529, 571, 573, 617, 660, 706, 710, 734, 758, 808, 833, 885, 891, 940
Offset: 1

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Comments

In Germany this is called the Number Shark (Zahlenhai) sequence: see the CrypTool link.
This sequence is associated with the taxman game. The open source cryptography e-learning program JCrypTool (JCT) includes a tutorial and a discussion about strategies for the taxman game. - Bernhard Esslinger, Mar 17 2015, Sep 17 2019 and May 04 2020
In order for a player to select a number in the game, at least one of the number's maximal factors must be available to be claimed by the taxman. - Brian Chess, Sep 24 2022

Crossrefs

Cf. A355079.

Programs

  • Haskell
    import Data.List ((\\), intersect)
    a019312 = t . enumFromTo 1 where
       t xs = foldl max 0 [z + t (xs \\ ds) | z <- xs,
                 let ds = a027750_row z, not $ null $ intersect xs $ init ds]
    -- Reinhard Zumkeller, Apr 05 2015

Formula

When you take a number from S, you must give all its proper divisors to the tax man and there must be at least one to give; T(S) is the maximum total income.

Extensions

Extended by Timothy Loh, Aug 12 2012
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