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A366723
a(n) = Sum_{k=1..n} (-1)^(k-1) * binomial(floor(n/k)+4,5).
4
1, 5, 21, 50, 121, 236, 447, 736, 1247, 1896, 2898, 4151, 5972, 8146, 11292, 14797, 19643, 25248, 32564, 40663, 51515, 63168, 78119, 94452, 114998, 136933, 164849, 193753, 229714, 268334, 314711, 362824, 422746, 483950, 558046, 635070, 726461, 820420, 934186, 1048245
OFFSET
1,2
FORMULA
a(n) = Sum_{k=1..n} binomial(k+3,4) * (floor(n/k) mod 2).
G.f.: -1/(1-x) * Sum_{k>=1} (-x)^k/(1-x^k)^5 = 1/(1-x) * Sum_{k>=1} binomial(k+3,4) * x^k/(1+x^k).
PROG
(PARI) a(n) = sum(k=1, n, (-1)^(k-1)*binomial(n\k+4, 5));
CROSSREFS
Partial sums of A366814.
Cf. A365439.
Sequence in context: A201279 A146721 A099979 * A039659 A147238 A316435
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 24 2023
STATUS
approved