A104510 - OEIS

%I #9 Aug 18 2017 03:12:48

%S 0,-1,2,-4,4,-7,4,-5,0,5,-18,23,-46,65,-82,108,-132,152,-164,168,-144,

%T 132,-48,-39,212,-365,658,-947,1382,-1800,2394,-2947,3644,-4289,5102,

%U -5687,6392,-6820,7112,-7139,6776,-5836,4338,-2036,-1342,5585,-11392,18513,-27456,37876,-51072,65488,-82982,101898

%N G.f.: Product_{i>=1} (1 - 2*(-x)^i)/(1 - (-x)^i)^2.

%F a(n) = Sum (k(1)-1)*(k(2)-1)*...*(k(n)-1), where the sum is taken over all (k(1), k(2), ..., k(n)) such that k(1) + 2*k(2) + ... + n*k(n) = n, k(i) >= 0, i=1..n.

%F G.f.: Product_{i>=1} (1 - (-x)^i)^A052823(i). - _James A. Sellers_, Apr 22 2005

%p gf:=product((1-2*(-x)^i)/(1-(-x)^i)^2, i=1..100): s:=series(gf, x, 100): for n from 1 to 99 do printf(`%d,`,coeff(s, x, n)) od: # _James A. Sellers_, Apr 22 2005

%Y Cf. A000712, A077285.

%Y Cf. A104575.

%K easy,sign

%O 1,3

%A _Vladeta Jovovic_, Apr 19 2005

%E More terms from _James A. Sellers_, Apr 22 2005