A161802 - OEIS

%I #4 Mar 30 2012 18:37:17

%S 2,-16,18,176,-544,-160,2834,-5104,3232,18032,-68992,48400,143074,

%T -343088,461344,63888,-2298880,2963520,1387424,-5145536,10416514,

%U -9297312,-31084704,42991712,34760672,-51170800,81567168,-94111088

%N G.f. is Q_1(q) where q*Q_1(q^4) is a series quadrisection of the g.f. of A161800.

%C The g.f. of A161800 has two nonzero series quadrisections; the other is given by A161801.

%e G.f.: Q_1(q) = 2 - 16*q + 18*q^2 + 176*q^3 - 544*q^4 - 160*q^5 + 2834*q^6 +...

%o (PARI) {a(n)=local(L=sum(m=1, 4*n+1,2*2^valuation(m,2)*sumdiv(m, d, -(-1)^d*d)*x^m/m)+x*O(x^(4*n+1))); polcoeff(exp(L), 4*n+1)}

%Y Cf. A161800, A161801.

%K sign

%O 0,1

%A _Paul D. Hanna_, Jul 19 2009