login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A055515 (2^n -1)/product(2^p -1) where the product is over all distinct primes p that divide n. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..43.

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

Sequence in context: A155059 A206076 A115638 * A215010 A136744 A068237

Adjacent sequences:  A055512 A055513 A055514 * A055516 A055517 A055518

KEYWORD

easy,nonn

AUTHOR

Leroy Quet, Jul 03 2000

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified October 21 00:03 EDT 2014. Contains 248371 sequences.