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A226265
Number of additive Z_2 Z_8 codes of a certain type (see Siap-Aydogdu for precise definition).
6
504, 1176, 2520, 5208, 10584, 21336, 42840, 85848, 171864, 343896, 687960, 1376088, 2752344, 5504856, 11009880, 22019928, 44040024, 88080216, 176160600, 352321368, 704642904, 1409285976, 2818572120, 5637144408, 11274288984, 22548578136, 45097156440
OFFSET
1,1
COMMENTS
N2×8(r+1, 3; r, 1, 1, 1) r>=1. (Siap-Aydogdu Table 1)
LINKS
I. Siap and I. Aydogdu, Counting The Generator Matrices of Z_2 Z_8 Codes, arXiv preprint arXiv:1303.6985 [math.CO], 2013.
FORMULA
Conjectures from Colin Barker, Jun 14 2017: (Start)
G.f.: 168*x*(3 - 2*x) / ((1 - x)*(1 - 2*x)).
a(n) = 168*(2^(1+n) - 1) for n>0.
a(n) = 3*a(n-1) - 2*a(n-2) for n>2.
(End)
MATHEMATICA
QP = QPochhammer;
a[n_] := 168 2^(n^2 + 4n) QP[2^(-n-1), 2, n]/(2^(n^2 + 3n) QP[2^-n, 2, n]);
Array[a, 27] (* Jean-François Alcover, Sep 01 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 02 2013
EXTENSIONS
Terms a(6) and beyond from Lars Blomberg, Jun 14 2017
STATUS
approved