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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A100312 Number of 3 X n binary matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (10;0) and (01;1).

Original entry on oeis.org

1, 8, 32, 104, 304, 832, 2176, 5504, 13568, 32768, 77824, 182272, 421888, 966656, 2195456, 4947968, 11075584, 24641536, 54525952, 120061952, 263192576, 574619648, 1249902592, 2709520384, 5855248384, 12616466432, 27111981056, 58116276224, 124285616128
Offset: 0

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Author

Sergey Kitaev, Nov 13 2004

Keywords

Comments

An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1 < i2, j1 < j2 and these elements are in the same relative order as those in the triple (x,y,z). In general, the number of m X n 0-1 matrices in question is given by the g.f. 2*x*y/(1-2*(x+y-x*y)).

Crossrefs

Cf. A049611, this sequence (m=3), A100313 (m=4).

Programs

  • Magma
    [2^(n-1)*(n^2+5*n+2): n in [0..50]]; // G. C. Greubel, Feb 01 2023
    
  • Mathematica
    Table[2^(n-1)*(n^2+5*n+2), {n,0,50}] (* G. C. Greubel, Feb 01 2023 *)
  • PARI
    vector(50, n, (n^2 + 5*n + 2) * 2^(n-1)) \\ Michel Marcus, Dec 01 2014
    
  • SageMath
    [2^(n-1)*(n^2+5*n+2) for n in range(51)] # G. C. Greubel, Feb 01 2023

Formula

G.f.: 1 + 8*x*(1-x)^2/(1-2*x)^3.
a(n) = 2^(n-1) * (n^2 + 5*n + 2).
a(n) = 8 * A049611(n) for n>0.
E.g.f.: (1 + 6*x + 2*x^2)*exp(2*x). - G. C. Greubel, Feb 01 2023

Extensions

a(0)=1 prepended by Alois P. Heinz, Dec 21 2018
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