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A367009
Number of divisors of n*2^n + 1.
2
1, 2, 3, 3, 4, 4, 8, 8, 4, 4, 12, 4, 8, 6, 8, 8, 4, 12, 16, 16, 16, 4, 16, 16, 16, 16, 24, 16, 6, 8, 48, 48, 8, 4, 32, 4, 12, 8, 12, 8, 8, 16, 16, 32, 16, 16, 32, 32, 16, 10, 64, 8, 64, 8, 32, 16, 12, 32, 32, 16, 16, 128, 8, 8, 96, 32, 256, 24, 16, 32, 32, 48
OFFSET
0,2
COMMENTS
The numbers n*2^n+1 are called Cullen numbers.
LINKS
FORMULA
a(n) = sigma0(n*2^n + 1) = A000005(A002064(n)).
MATHEMATICA
Table[DivisorSigma[0, n*2^n + 1], {n, 0, 100}] (* Amiram Eldar, Jan 06 2024 *)
PROG
(PARI) a(n) = numdiv(n*2^n + 1); \\ Amiram Eldar, Jan 06 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 31 2023
STATUS
approved