A131237 - OEIS

%I #8 Aug 26 2015 00:34:44

%S 1,6,79,1837,66021,3374176,231848191,20570267229,2285620096717,

%T 310524073877026,50598503336716611,9732804817777566361,

%U 2180831456691952213969,562835395375423511668692,165687992856606963112408291,55166524646338775672718351481,20620925283916296038124156761241

%N Number of n X (n+1) matrices with nonnegative integer entries and every row and column sum <= 2.

%D R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.65(a).

%p A131237 := proc(n)

%p         exp((x*y*(3-x*y)/2+(x+y)*(2-x*y)/2)/(1-x*y))/sqrt(1-x*y) ;

%p         coeftayl(%,y=0,n+1) ;

%p         coeftayl(%,x=0,n) ;

%p         %*(n+1)!*n! ;

%p         simplify(%) ;

%p end proc: # _R. J. Mathar_, Sep 30 2011

%Y Cf. A049088, A131235, A131236.

%K easy,nonn

%O 0,2

%A _Vladeta Jovovic_, Jun 20 2007