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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A076506 Expansion of x*(1+3*x+12*x^2)/(1-24*x^3).

Original entry on oeis.org

1, 3, 12, 24, 72, 288, 576, 1728, 6912, 13824, 41472, 165888, 331776, 995328, 3981312, 7962624, 23887872, 95551488, 191102976, 573308928, 2293235712, 4586471424, 13759414272, 55037657088, 110075314176, 330225942528
Offset: 1

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Author

Jon Perry, Oct 15 2002

Keywords

Comments

Previous name was: 3 people at a party are saying Hello to each other. Person 1 says Hello. Person 2 counts the times Hello has been said and says Hello twice that number of times. Person 3 says Hello 3 times the sum of Hello's and then it is Person 1's turn again. This is how the sum of Hello's.

Links

Crossrefs

Cf. A076505.

Programs

  • Mathematica
    a[n_] := Product[Mod[k, 3]+2, {k, 1, n-1}]; Array[a, 26] (* Jean-François Alcover, Oct 05 2016, adapted from PARI *)
  • PARI
    a(n)=prod(k=1,n-1,k%3+2)

Formula

G.f.: x*(1+3*x+12*x^2)/(1-24*x^3). [Colin Barker, Jun 07 2012]
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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