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

Offset: 1

Author

Reinhard Zumkeller, Nov 01 2012

Keywords

• nonn

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

Crossrefs

Cf. A000961, A010055, A027750.

Cf. A000668.

Programs

Haskell

a185208 n = a185208_list !! (n-1)
a185208_list =  filter ((== 1) . a141197) [1..]

Mathematica

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