OFFSET
0,9
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,1,0,1,0,1).
FORMULA
G.f: 1/(1-x^3-x^5-x^7).
a(n) = a(n-3) + a(n-5) + a(n-7).
EXAMPLE
a(16) = 10: the compositions are the permutations of [5533] (there are 4!/2!2!=6 of them) and the permutations of [7333] (there are 4!/3!=4).
MATHEMATICA
LinearRecurrence[{0, 0, 1, 0, 1, 0, 1}, {1, 0, 0, 1, 0, 1, 1}, 70] (* Harvey P. Dale, Jan 27 2017 *)
PROG
(PARI) Vec(1/(1-x^3-x^5-x^7) +O(x^66)) \\ Joerg Arndt, Aug 20 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
David Neil McGrath, Aug 20 2014
STATUS
approved