login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A242016 Smallest prime factor of A135972(n), the n-th composite Mersenne number. 2
3, 3, 3, 7, 3, 23, 3, 3, 7, 3, 3, 3, 7, 3, 47, 3, 31, 3, 7, 3, 233, 3, 3, 7, 3, 31, 3, 223, 3, 7, 3, 13367, 3, 431, 3, 7, 3, 2351, 3, 127, 3, 7, 3, 6361, 3, 23, 3, 7, 3, 179951, 3, 3, 7, 3, 31, 3, 193707721, 3, 7, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..1201

FORMULA

a(n) = A020639(A135972(n)).

PROG

(PARI) for(n=2, 1e2, if(!ispseudoprime(2^n-1), p=factor(2^n-1)[1, 1]; print1(p, ", ")))

CROSSREFS

Cf. A135972, A242017. Subsequence of A056608.

Sequence in context: A291767 A135087 A294505 * A084038 A326930 A095108

Adjacent sequences:  A242013 A242014 A242015 * A242017 A242018 A242019

KEYWORD

nonn

AUTHOR

Felix Fröhlich, Aug 11 2014

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 23 03:22 EDT 2020. Contains 337291 sequences. (Running on oeis4.)