OFFSET
0,2
FORMULA
a(n) = 2^n * A000005(n) for n > 0, a(0) = 1.
G.f.: 1 + Sum_{k>=1} 2^k*x^k/(1 - 2^k*x^k). - Ilya Gutkovskiy, May 23 2019
EXAMPLE
The a(3) = 16 matrices:
[000] [001] [010] [011] [100] [101] [110] [111]
.
[0] [0] [0] [0] [1] [1] [1] [1]
[0] [0] [1] [1] [0] [0] [1] [1]
[0] [1] [0] [1] [0] [1] [0] [1]
MATHEMATICA
Table[2^n*DivisorSigma[0, n], {n, 10}]
PROG
(PARI) a(n) = if (n==0, 1, 2^n*numdiv(n)); \\ Michel Marcus, Jan 15 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 15 2019
STATUS
approved