OFFSET
0,9
FORMULA
G.f. A(x) satisfies: A(x) = (1 + x^4 * A(x)^2) / (1 - x + x^4 + x^5 + x^6 + x^7). - Ilya Gutkovskiy, Jul 20 2021
MAPLE
A023430 := proc(n)
option remember;
if n = 0 then
1;
else
procname(n-1)+add(procname(k)*procname(n-4-k), k=4..n-4) ;
end if;
end proc: # R. J. Mathar, May 01 2015
MATHEMATICA
Clear[ a ]; a[ 0 ]=1; a[ n_Integer ] := a[ n ]=a[ n-1 ]+Sum[ a[ k ]*a[ n-4-k ], {k, 4, n-4} ];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Sean A. Irvine, Jun 04 2019
STATUS
approved