A278406 G.f.: x^2 * f''(x), where f(x) = Product_{k>=1} 1 / (1 - x^k).

0, 0, 4, 18, 60, 140, 330, 630, 1232, 2160, 3780, 6160, 10164, 15756, 24570, 36960, 55440, 80784, 117810, 167580, 238260, 332640, 462924, 635030, 869400, 1174800, 1583400, 2113020, 2810808, 3706780, 4875480, 6363060, 8282208, 10711008, 13811820, 17710770

Offset

0,3

Links

Seiichi Manyama, Table of n, a(n) for n = 0..10000

Formula

a(n) = n*(n-1)*A000041(n).

Mathematica

nmax=60; CoefficientList[Series[x^2*D[Product[1/(1-x^k), {k, 1, nmax}], {x, 2}], {x, 0, nmax}], x]
nmax=60; CoefficientList[Series[Product[1/(1-x^k), {k, 1, nmax}], {x, 0, nmax}], x]*Range[0, nmax]*(Range[0, nmax]-1)

Crossrefs

Cf. A000041, A066186, A066189, A278407.

Sequence in context: A058851 A167885 A212521 * A192069 A073373 A292465

Adjacent sequences: A278403 A278404 A278405 * A278407 A278408 A278409

Keyword

nonn

Author

Vaclav Kotesovec, Nov 21 2016

Status

approved