A014696 - OEIS

A014696

Poincaré series [or Poincare series] (or Molien series) for mod 2 cohomology of universal W-group W(3).

1, 3, 14, 30, 77, 138, 273, 438, 748, 1113, 1729, 2436, 3542, 4788, 6630, 8676, 11571, 14751, 19096, 23826, 30107, 36894, 45695, 55146, 67158, 79989, 96019, 113064, 134044, 156264, 183260, 211752, 245973, 281979, 324786, 369702, 422617, 478002

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..37.

A. Adem, Recent developments in the cohomology of finite groups, Notices Amer. Math. Soc., 44 (1997), 806-812.

Index entries for two-way infinite sequences

Index entries for linear recurrences with constant coefficients, signature (2,3,-8,-2,12,-2,-8,3,2,-1).

FORMULA

G.f.: (1+x+5x^2+x^3+x^4)/((1-x)^2*(1-x^2)^4). a(n)=-a(-6-n).

MAPLE

(x^4+x^3+5*x^2+x+1)/(x-1)^2/(-1+x^2)^4;

MATHEMATICA

LinearRecurrence[{2, 3, -8, -2, 12, -2, -8, 3, 2, -1}, {1, 3, 14, 30, 77, 138, 273, 438, 748, 1113}, 40] (* Harvey P. Dale, Sep 24 2017 *)

PROG

(PARI) a(n)=n+=3; n*((18*n^4-70*n^2+97)-(50*n^2-95)*(-1)^n)/3840

CROSSREFS

Sequence in context: A256053 A354041 A031049 * A235137 A197944 A071396

Adjacent sequences: A014693 A014694 A014695 * A014697 A014698 A014699

KEYWORD

nonn,easy

AUTHOR

Alejandro Adem (adem(AT)math.wisc.edu)

STATUS

approved