A005880 Theta series of D_4 lattice with respect to edge. (Formerly M1827)

2, 8, 12, 16, 26, 24, 28, 48, 36, 40, 64, 48, 62, 80, 60, 64, 96, 96, 76, 112, 84, 88, 156, 96, 114, 144, 108, 144, 160, 120, 124, 208, 168, 136, 192, 144, 148, 248, 192, 160, 242, 168, 216, 240

Offset

0,1

References

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

G. C. Greubel, Table of n, a(n) for n = 0..5000

Index entries for sequences related to D_4 lattice

Formula

Empirical: Sum_{n>=0} a(n) / exp(n*Pi) = (1/4) * exp(Pi / 2) * Pi * sqrt(2) / Gamma(3/4)^4 = A388170. - Simon Plouffe, Sep 15 2025

Mathematica

Table[2 DivisorSigma[1, 2 n + 1], {n, 0, 43}] (* Jean-François Alcover, Jul 06 2017 *)

Prog

(PARI) for(n=0, 30, print1(2*sigma(2*n+1), ", ")) \\ G. C. Greubel, Nov 30 2017

Crossrefs

Equals 2 * A008438.

Sequence in context: A285658 A284802 A067884 * A290608 A340690 A303900

Adjacent sequences: A005877 A005878 A005879 * A005881 A005882 A005883

Keyword

nonn

Author

N. J. A. Sloane

Status

approved