OFFSET
0,2
FORMULA
PROG
(PARI) a(n)=local(A=Mat(1), B); for(m=1, n+2, 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+2, 2])
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 29 2007
STATUS
approved