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A376711
G.f.: Sum_{k>=0} x^(k*(k+1)) * Product_{j=1..k} 1/(1 - x^j)^4.
1
1, 0, 1, 4, 10, 20, 36, 60, 98, 156, 250, 396, 631, 992, 1555, 2400, 3673, 5536, 8265, 12176, 17781, 25692, 36846, 52404, 74080, 104028, 145344, 201972, 279420, 384764, 527696, 720668, 980482, 1328728, 1794118, 2413520, 3235440, 4321968, 5754108, 7635276, 10099310
OFFSET
0,4
FORMULA
a(n) ~ exp(2*Pi*sqrt(2*n/5)) / (4 * 5^(5/4) * n^(3/2)).
MATHEMATICA
nmax = 40; CoefficientList[Series[Sum[x^(k*(k+1))/Product[1-x^j, {j, 1, k}]^4, {k, 0, Sqrt[nmax]}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vaclav Kotesovec, Oct 02 2024
STATUS
approved