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

1,2

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

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

Crossrefs

Cf. A000961, A010055, A027750.

Cf. A000668.

Sequence in context: A206548 A206547 A295584 * A216227 A020611 A156312

Adjacent sequences: A185205 A185206 A185207 * A185209 A185210 A185211

Keyword

nonn

Author

Reinhard Zumkeller, Nov 01 2012

Status

approved