0,2

(PARI) {a(n)=local(A=Mat(1), B); for(m=1, n+3, B=matrix(m, m); for(r=1, m, for(c=1, r, if(r==c|r==1|r==2, B[r, c]=1, if(c==1, B[r, 1]=sum(i=1, r-1, A[r-1, i]), B[r, c]=(A^(2^(c-1)))[r-c+1, 1])); )); A=B); return(A[n+3, 3])}

Cf. A129100 (triangle); A129092 (column 0), A129101 (column 1), A129103 (column 3).

Sequence in context: A038173 A143463 A141716 this_sequence A129099 A098541 A004204

Adjacent sequences: A129099 A129100 A129101 this_sequence A129103 A129104 A129105

nonn

Paul D. Hanna (pauldhanna(AT)juno.com), Mar 29 2007