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A163318
Expansion of g.f.: Product_{k>=1} 1+k*x^k/(1-x^k)^2.
2
1, 1, 4, 8, 19, 36, 76, 142, 272, 496, 900, 1592, 2784, 4792, 8138, 13688, 22703, 37380, 60838, 98310, 157298, 250162, 394332, 618032, 961512, 1487563, 2286610, 3496776, 5316666, 8044598, 12110538, 18147166, 27068692, 40203306, 59459998, 87587428, 128522850
OFFSET
0,3
LINKS
MAPLE
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
b(n, i-1) +add(b(n-i*j, i-1)*(j*i), j=1..n/i)))
end:
a:= n-> b(n, n):
seq(a(n), n=0..40); # Alois P. Heinz, Feb 25 2013
MATHEMATICA
terms = 40;
CoefficientList[Product[1 + k x^k/(1 - x^k)^2, {k, 1, terms}] + O[x]^terms, x] (* Jean-François Alcover, Nov 12 2020 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Jul 24 2009
STATUS
approved