A369875 a(n) = [x^n] Product_{d|n} (x^d + 1 + 1/x^d).
1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 19, 1, 1, 1, 1, 1, 11, 1, 11, 1, 1, 1, 85, 1, 1, 1, 6, 1, 64, 1, 1, 1, 1, 1, 145, 1, 1, 1, 54, 1, 41, 1, 1, 5, 1, 1, 382, 1, 1, 1, 1, 1, 34, 1, 34, 1, 1, 1, 2425, 1, 1, 3, 1, 1, 27, 1, 1, 1, 23, 1, 1943, 1, 1, 1, 1, 1, 20, 1, 225
Offset: 1
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..20000
Programs
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Mathematica
Table[Coefficient[Product[(x^d + 1 + 1/x^d), {d, Divisors[n]}], x, n], {n, 1, 80}] -
Python
from collections import Counter from sympy import divisors def A369875(n): c = {0:1} for d in divisors(n,generator=True): b = Counter(c) for j in c: a = c[j] b[j+d] += a b[j-d] += a c = b return c[n] # Chai Wah Wu, Feb 05 2024
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