A185208 - OEIS

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A185208

Numbers having no divisors d > 1 such that d + 1 are prime powers.

1, 5, 11, 13, 17, 19, 23, 25, 29, 37, 41, 43, 47, 53, 55, 59, 61, 65, 67, 71, 73, 79, 83, 85, 89, 95, 97, 101, 103, 107, 109, 113, 115, 121, 125, 131, 137, 139, 143, 145, 149, 151, 157, 163, 167, 169, 173, 179, 181, 185, 187, 191, 193, 197, 199, 205, 209

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OFFSET

1,2

COMMENTS

A141197(a(n)) = A049073(a(n)) = 1.

Contains all primes except for 2 and Mersenne primes A000668. - Jon Perry, Nov 11 2012

A composite number is in the sequence iff all its factors are. - Jon Perry, Nov 11 2012

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Range[210], Select[Divisors[#] // Rest, PrimeNu[# + 1] == 1 &] == {} &] (* Jean-François Alcover, Aug 17 2013 *)

PROG