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A099770 Expansion of 1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)). 1
1, 1, 2, 2, 4, 4, 7, 7, 11, 11, 16, 16, 23, 23, 31, 31, 41, 41, 53, 53, 67, 67, 83, 83, 102, 102, 123, 123, 147, 147, 174, 174, 204, 204, 237, 237, 274, 274, 314, 314, 358, 358, 406, 406, 458, 458, 514, 514, 575, 575, 640, 640, 710, 710, 785, 785, 865, 865, 950, 950, 1041, 1041 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Molien series for symmetrized weight enumerators of Hermitian self-dual codes over the Galois ring GR(4,2).

Number of partitions of n into parts 1, 2, 4, and 6. - Joerg Arndt, May 05 2014

a(n) is equal to the number of partitions of degree at most n+6 of length 3 with even entries. - John M. Campbell, Jan 20 2016

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

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

Index entries for Molien series

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

FORMULA

a(n) ~ 1/288*n^3. - Ralf Stephan, Apr 29 2014

It appears that a(n) = (2*n^3 +39*n^2 +241*n +372 +3*(n^2 +13*n +40) * (-1)^n -84*(-1)^((2*n +3 +(-1)^n)/4) -192*floor(((2*n +9 +(-1)^n-6*(-1)^((2*n+3+(-1)^n)/4))/24)))/576. - Luce ETIENNE, May 05 2014

EXAMPLE

From John M. Campbell, Jan 20 2016: (Start)

Letting n=6, a(n) = 7 is equal to the number of partitions of n into parts 1, 2, 4, and 6, as illustrated below, and a(n) is equal to the number of partitions of degree at most n+6 of length 3 with even entries, as illustrated below. The arrows below illustrate a natural bijection between the set of partitions of the former form and the set of partitions of the latter form.

(2, 2, 2) <-> (1, 1, 1, 1, 1, 1)

(4, 2, 2) <-> (2, 1, 1, 1, 1)

(6, 2, 2) <-> (4, 1, 1)

(4, 4, 2) <-> (2, 2, 1, 1)

(8, 2, 2) <-> (6)

(6, 4, 2) <-> (4, 2)

(4, 4, 4) <-> (2, 2, 2)

(End)

MAPLE

seq(coeff(series(1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)), x, n+1), x, n), n = 0 .. 65); # G. C. Greubel, Sep 04 2019

MATHEMATICA

CoefficientList[Series[1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)), {x, 0, 65}], x] (* G. C. Greubel, Sep 04 2019 *)

PROG

(PARI) Vec(1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)) + O(x^80)) \\ Michel Marcus, Jan 21 2016

(MAGMA) R<x>:=PowerSeriesRing(Integers(), 65); Coefficients(R!( 1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6)) )); // G. C. Greubel, Sep 04 2019

(Sage)

def A099770_list(prec):

    P.<x> = PowerSeriesRing(ZZ, prec)

    return P(1/((1-x)*(1-x^2)*(1-x^4)*(1-x^6))).list()

A099770_list(65) # G. C. Greubel, Sep 04 2019

(GAP) a:=[1, 1, 2, 2, 4, 4, 7, 7, 11, 11, 16, 16, 23];; for n in [14..65] do a[n]:= a[n-1]+a[n-2]-a[n-3]+a[n-4]-a[n-5]-a[n-8]+a[n-9]-a[n-10]+a[n-11]+a[n-12] -a[n-13]; od; a; # G. C. Greubel, Sep 04 2019

CROSSREFS

Cf. A000601.

Sequence in context: A341951 A182410 A341719 * A099383 A341972 A277133

Adjacent sequences:  A099767 A099768 A099769 * A099771 A099772 A099773

KEYWORD

nonn

AUTHOR

G. Nebe (nebe(AT)math.rwth-aachen.de), Nov 10 2004

STATUS

approved

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Last modified August 5 15:11 EDT 2021. Contains 346471 sequences. (Running on oeis4.)