OFFSET
0,13
COMMENTS
Number of compositions of n into parts 5 and 7.
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,1,0,1).
FORMULA
a(n) = a(n-5) + a(n-7).
Gf.: 1/((1-x+x^2)*(1+x-x^3-x^4-x^5)) . - R. J. Mathar, Jul 03 2024
PROG
(PARI) my(N=80, x='x+O('x^N)); Vec(1/(1-x^5-x^7))
(PARI) a(n) = sum(k=0, n\7, ((n-2*k)%5==0)*binomial((n-2*k)/5, k));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Feb 02 2024
STATUS
approved