OFFSET
0,2
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,0,1).
FORMULA
a(n) = a(n-1) + a(n-5) + a(n-7) + delta(n,0) + delta(n,1) + delta(n,2) + 2*delta(n,3) + 2*delta(n,4) + delta(n,5) + delta(n,6), a(n<0) = 0.
G.f.: (1 + x + x^2 + 2*x^3 + 2*x^4 + x^5 + x^6)/(1 - x - x^5 - x^7).
EXAMPLE
When n = 5, the 9 subsets are {}, {1}, {2}, {3}, {4}, {5}, {1,3}, {2,4}, and {3,5}.
MATHEMATICA
CoefficientList[Series[(1 + x + x^2 + 2x^3 + 2x^4 + x^5 + x^6)/(1 - x - x^5 - x^7), {x, 0, 45}], x]
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Michael A. Allen, Feb 22 2022
STATUS
approved