0,2

(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^3)[n+2, 2])}

Cf. A135888, A135889; A135880, A135895.

Sequence in context: A122827 A103194 A009018 this_sequence A067273 A137972 A007322

Adjacent sequences: A135887 A135888 A135889 this_sequence A135891 A135892 A135893

nonn

Paul D. Hanna (pauldhanna(AT)juno.com), Dec 15 2007