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A188216 Expansion of 1 + Sum_{n>=1} (x^(n^2) / Product_{k>=n} (1 - x^k)). 5
1, 1, 1, 2, 4, 5, 8, 12, 17, 25, 34, 46, 64, 86, 114, 151, 200, 258, 335, 431, 552, 703, 891, 1121, 1411, 1764, 2196, 2725, 3374, 4155, 5111, 6260, 7650, 9319, 11329, 13726, 16608, 20031, 24114, 28962, 34725, 41529, 49595, 59095, 70304, 83476, 98968, 117109 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
COMMENTS
Number of partitions of n such that if k is the least part, then k occurs at least k times. - Joerg Arndt, Apr 17 2011
LINKS
MAPLE
b:= proc(n, i) option remember; `if`(n=0, 1,
`if`(i>n, 0, b(n, i+1)+b(n-i, i)))
end:
a:= n-> `if`(n=0, 1, add(b(n-j^2, j), j=1..isqrt(n))):
seq(a(n), n=0..50); # Alois P. Heinz, Jan 03 2021
MATHEMATICA
b[n_, i_] := b[n, i] = If[n==0, 1, If[i>n, 0, b[n, i+1] + b[n-i, i]]];
a[n_] := If[n==0, 1, Sum[b[n - j^2, j], {j, 1, Sqrt[n]}]];
a /@ Range[0, 50] (* Jean-François Alcover, Jan 25 2021, after Alois P. Heinz *)
PROG
(PARI) N=55; x='x+O('x^N);
t=1+sum(n=1, N, x^(n^2)/prod(k=n, N, 1-x^k));
Vec(t)
CROSSREFS
Cf. A096403 (expansion of sum(n>=1, x^(n^2) / prod(k>=n+1, 1-x^k)) ).
Cf. A003114 (largest part k occurs at least k times).
Sequence in context: A069259 A102186 A039842 * A238395 A116901 A350846
KEYWORD
nonn
AUTHOR
Joerg Arndt, Mar 24 2011
STATUS
approved

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Last modified March 28 05:02 EDT 2024. Contains 371235 sequences. (Running on oeis4.)