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The even bisection of A000594.
1

%I #8 Apr 17 2015 11:53:25

%S -24,-1472,-6048,84480,-115920,-370944,401856,987136,2727432,-7109760,

%T -12830688,21288960,13865712,24647168,-29211840,-196706304,165742416,

%U 167282496,-255874080,408038400,101267712,-786948864,-447438528,248758272,611981400,850430336,1758697920

%N The even bisection of A000594.

%F a(n) = A000594(2*n). - _Michael Somos_, Apr 17 2015

%e G.f. = -24*x - 1472*x^2 - 6048*x^3 + 84480*x^4 - 115920*x^5 - 370944*x^6 + ...

%e G.f. = -24*q^2 - 1472*q^4 - 6048*q^6 + 84480*q^8 - 115920*q^10 - 370944*q^12 + ...

%t a[ n_] := SeriesCoefficient[ q QPochhammer[q]^24, {q, 0, 2 n}]; (* _Michael Somos_, Apr 17 2015 *)

%o (PARI) {a(n) = if( n<0, 0, n = 2*n; polcoeff( x * eta(x + x * O(x^n))^24, n))}; /* _Michael Somos_, Apr 17 2015 */

%Y Cf. A000594.

%K sign

%O 1,1

%A _N. J. A. Sloane_, Nov 15 2004

%E More terms from _Joshua Zucker_, May 15 2006