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A366898
Number of divisors of n*2^n - 1, the Woodall (or Riesel) numbers.
4
1, 2, 2, 6, 4, 2, 4, 4, 4, 4, 6, 4, 12, 10, 8, 48, 8, 4, 8, 4, 16, 16, 8, 8, 4, 8, 8, 16, 24, 2, 8, 4, 8, 32, 8, 32, 4, 8, 4, 24, 16, 8, 32, 8, 16, 24, 40, 16, 16, 8, 8, 16, 24, 8, 16, 8, 16, 6, 32, 8, 8, 16, 8, 512, 48, 16, 12, 48, 16, 8, 8, 4, 24, 16, 2, 256
OFFSET
1,2
LINKS
FORMULA
a(n) = sigma0(n*2^n - 1) = A000005(A003261(n)).
MATHEMATICA
Table[DivisorSigma[0, n*2^n - 1], {n, 1, 100}] (* Amiram Eldar, Dec 11 2023 *)
PROG
(PARI) a(n) = numdiv(n*2^n - 1); \\ Amiram Eldar, Dec 11 2023
KEYWORD
nonn
AUTHOR
Tyler Busby, Oct 26 2023
STATUS
approved