A055515 a(n) = (2^n - 1)/product(2^p - 1) where the product is over all distinct primes p that divide n.

1, 1, 1, 5, 1, 3, 1, 85, 73, 11, 1, 195, 1, 43, 151, 21845, 1, 12483, 1, 11275, 2359, 683, 1, 798915, 1082401, 2731, 19173961, 704555, 1, 1649373, 1, 1431655765, 599479, 43691, 8727391, 3272356035, 1, 174763, 9588151, 11822705675, 1, 1649061309, 1

Offset

1,4

Links

John Tyler Rascoe, Table of n, a(n) for n = 1..1000

Formula

For p prime, a(p) = 1. - Michel Marcus, May 18 2014

For p prime, a(p^2) = A051156(n). - Michel Marcus, May 18 2014

Example

a(12) = (2^12 -1)/((2^2 -1) (2^3 -1)) = 195.

Prog

(PARI) a(n) = my(f = factor(n)); (2^n-1)/prod(i=1, #f~, 2^f[i, 1] -1); \\ Michel Marcus, May 18 2014

Crossrefs

Cf. A055977.

Sequence in context: A329374 A115638 A342375 * A363437 A338096 A215010

Adjacent sequences: A055512 A055513 A055514 * A055516 A055517 A055518

Keyword

easy,nonn,changed

Author

Leroy Quet, Jul 03 2000

Status

approved