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%I A135887 #2 Mar 30 2012 18:37:07
%S A135887 1,6,42,351,3470,39968,528306,7906598,132426050,2457643895,
%T A135887 50110693656,1114365815786,26856942480503,697612318151050,
%U A135887 19435260247394150,578255661792065917,18303904706366202568,614296560055922433760
%N A135887 Column 2 of triangle Q = A135885; also equals column 0 of Q^3 = A135893.
%e A135887 Triangle Q = A135885 begins:
%e A135887 1;
%e A135887 2, 1;
%e A135887 6, 4, 1;
%e A135887 25, 20, 6, 1;
%e A135887 138, 126, 42, 8, 1;
%e A135887 970, 980, 351, 72, 10, 1;
%e A135887 8390, 9186, 3470, 748, 110, 12, 1; ...
%e A135887 where column k of Q equals column 0 of Q^(k+1) such that
%e A135887 column 0 of Q equals column 0 of P=A135880 shift left and Q=P^2.
%o A135887 (PARI) {a(n)=local(P=Mat(1),R,PShR);if(n==0,1,for(i=0,n+1, PShR=matrix(#P,#P, r,c, if(r>=c,if(r==c,1,if(c==1,0,P[r-1,c-1]))));R=P*PShR; R=matrix(#P+1, #P+1, r,c, if(r>=c, if(r<#P+1,R[r,c], if(c==1,(P^2)[ #P,1],(P^(2*c-1))[r-c+1,1])))); P=matrix(#R, #R, r,c, if(r>=c, if(r<#R,P[r,c], (R^c)[r-c+1,1]))));(P^2)[n+3,3])}
%Y A135887 Cf. A135885 (Q), A135893 (Q^3), A135880; other columns: A135881, A135886.
%K A135887 nonn
%O A135887 0,2
%A A135887 _Paul D. Hanna_, Dec 15 2007

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