0,2

Number of 3 X n binary matrices avoiding simultaneously the right angled numbered polyomino patterns (ranpp) (00;1), (01,1) and (11;0). 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 (n+2)*2^(m-1)+2*m*(n-1)-2 for m>1 and n>1. - Sergey Kitaev (kitaev(AT)ms.uky.edu), Nov 12 2004

If Y is a 5-subset of an n-set X then, for n>=5, a(n-4) is the number of 3-subsets of X having at least two elements in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Dec 08 2007

Tanya Khovanova, Recursive Sequences

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 322

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, Integers: Electronic Journal of Combinatorial Number Theory 4 (2004), A21, 20pp.

with(finance):seq(add(cashflows([3, 3, 4], 0 ), k=1..n), n=0..41); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 21 2008

(Other) sage: [i for i in range(420) if gcd(i, 10) == 10] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 20 2009]

Sequence in context: A057169 A096092 A109597 this_sequence A158814 A118959 A043489

Adjacent sequences: A008589 A008590 A008591 this_sequence A008593 A008594 A008595

nonn

N. J. A. Sloane (njas(AT)research.att.com).