A184269 Number of distinct n X 7 toroidal binary arrays.

20, 1182, 99880, 9587580, 981706832, 104715443852, 11488774559744, 1286742755471400, 146402730743793240, 16865594582168158776, 1962541914958813595480, 230271584688553159320640, 27207473390887478569212080, 3233802551602631768613571584

Offset: 1

Author

R. H. Hardin, Jan 10 2011

Keywords

• nonn

Links

• Vaclav Kotesovec, Table of n, a(n) for n = 1..470
• S. N. Ethier, Counting toroidal binary arrays, arXiv preprint arXiv:1301.2352, 2013 and J. Int. Seq. 16 (2013) #13.4.7.

Crossrefs

Column 7 of A184271.

Programs

Maple

with(numtheory):
a:= n-> add(add(phi(c)*phi(d) *2^(7*n/ilcm(c, d)),
        d=divisors(n)), c=[1,7])/(7*n):
seq(a(n), n=1..20);  # Alois P. Heinz, Aug 25 2012

Formula

a(n) ~ 128^n / (7*n). - Vaclav Kotesovec, Sep 04 2014

Extensions

More terms from Alois P. Heinz, Aug 25 2012