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A369345 a(n) is the constant term in expansion of Product_{k=1..n} (x^(k^3) + 1 + 1/x^(k^3)). 3
1, 1, 1, 1, 1, 1, 3, 3, 5, 17, 31, 61, 139, 309, 701, 1651, 3849, 8929, 22295, 53777, 131025, 335619, 837999, 2107947, 5484373, 14071891, 36275323, 95881995, 250956301, 659257445, 1763642977, 4685724391, 12496708267, 33766814039, 90846586161, 245197523769 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,7
COMMENTS
All terms are odd.
LINKS
MAPLE
b:= proc(n, i) option remember; `if`(n>(i*(i+1)/2)^2, 0,
`if`(i=0, 1, b(n, i-1)+b(n+i^3, i-1)+b(abs(n-i^3), i-1)))
end:
a:= n-> b(0, n):
seq(a(n), n=0..35); # Alois P. Heinz, Jan 21 2024
MATHEMATICA
Table[Coefficient[Product[x^(k^3) + 1 + 1/x^(k^3), {k, 1, n}], x, 0], {n, 0, 33}]
CROSSREFS
Sequence in context: A139431 A351639 A351638 * A144423 A128636 A123633
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jan 20 2024
STATUS
approved

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Last modified May 21 00:01 EDT 2024. Contains 372720 sequences. (Running on oeis4.)