OFFSET
0,2
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)).
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, Integers: Electronic Journal of Combinatorial Number Theory 4 (2004), A21, 20pp.
Index entries for linear recurrences with constant coefficients, signature (6,-12,8).
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
MATHEMATICA
Table[2^(n-1)*(n^2+5*n+2), {n, 0, 50}] (* G. C. Greubel, Feb 01 2023 *)
PROG
(PARI) vector(50, n, (n^2 + 5*n + 2) * 2^(n-1)) \\ Michel Marcus, Dec 01 2014
(Magma) [2^(n-1)*(n^2+5*n+2): n in [0..50]]; // G. C. Greubel, Feb 01 2023
(SageMath) [2^(n-1)*(n^2+5*n+2) for n in range(51)] # G. C. Greubel, Feb 01 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Sergey Kitaev, Nov 13 2004
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Dec 21 2018
STATUS
approved