OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..28
FORMULA
a(n) = [x^(7^n)] 1/Product_{j>=0}(1-x^(7^j)).
PROG
(PARI) a(n, q=7)=local(A=Mat(1), B); if(n<0, 0, for(m=1, n+2, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i || j==1, B[i, j]=1, B[i, j]=(A^q)[i-1, j-1]); )); A=B); return(sum(k=0, n, A[n+1, k+1])))
CROSSREFS
KEYWORD
nonn
AUTHOR
Gottfried Helms and Paul D. Hanna, Aug 22 2005
STATUS
approved