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A028309 Molien series for ring of symmetrized weight enumerators of self-dual codes (with respect to Euclidean inner product) of length n over GF(4). 0
1, 1, 2, 3, 5, 6, 9, 11, 15, 18, 23, 27, 33, 38, 45, 51, 59, 66, 75, 83, 93, 102, 113, 123, 135, 146, 159, 171, 185, 198, 213, 227, 243, 258, 275, 291, 309, 326, 345, 363, 383, 402, 423, 443, 465, 486, 509, 531, 555 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..48.

G. Nebe, E. M. Rains and N. J. A. Sloane, Self-Dual Codes and Invariant Theory, Springer, Berlin, 2006.

E. M. Rains and N. J. A. Sloane, Self-dual codes, pp. 177-294 of Handbook of Coding Theory, Elsevier, 1998 (Abstract, pdf, ps).

Index entries for Molien series

Index entries for linear recurrences with constant coefficients, signature (2,0,-2,1).

FORMULA

G.f.: (x^6 - x^5 + x^3 - x + 1)/((1-x)^2 * (1-x^2)). - Ralf Stephan, Apr 29 2014

a(n) = (1/8) * (2*n^2 + 3*(-1)^n + 6*n + 4). - Ralf Stephan, Apr 29 2014

MATHEMATICA

LinearRecurrence[{2, 0, -2, 1}, {1, 1, 2, 3, 5, 6, 9}, 50] (* Harvey P. Dale, Nov 06 2016 *)

CROSSREFS

Sequence in context: A239010 A104738 A319469 * A242717 A026810 A001400

Adjacent sequences:  A028306 A028307 A028308 * A028310 A028311 A028312

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 15 11:03 EDT 2018. Contains 316224 sequences. (Running on oeis4.)