A113990 - OEIS

A113990

Column 1 of triangle A113988, which is the matrix square of A113983: a(n) = [A113983^2](n+1,1).

%I #5 Jun 13 2017 23:38:15

%S 1,4,12,36,116,416,1680,7656,39256,225348,1439868,10179116,79153484,

%T 673262240,6231517920,62461031920,675005395152,7832909636740,

%U 97238472215564,1286967352638292,18102901048062404,269852768731391808

%N Column 1 of triangle A113988, which is the matrix square of A113983: a(n) = [A113983^2](n+1,1).

%o (PARI) a(n)=local(A,B);A=Mat(1);for(m=2,n+2,B=matrix(m,m); for(i=1,m, for(j=1,i,if(i<3 || j==1 || j==i,B[i,j]=1, B[i,j]=A[i-1,j-1]+(A^2)[i-2,j-1] );));A=B);(A^2)[n+2,2]

%Y Cf. A113988, A113989 (column 0), A113991 (column 2), A113992 (column 3).

%K nonn

%O 0,2

%A _Paul D. Hanna_, Nov 12 2005