A120430 Greater of prime powers that differ by 1. In other words, numbers k such that k-1 and k are prime powers.

2, 3, 4, 5, 8, 9, 17, 32, 128, 257, 8192, 65537, 131072, 524288, 2147483648, 2305843009213693952, 618970019642690137449562112, 162259276829213363391578010288128

Offset

1,1

Comments

See comments in A006549.

Links

Table of n, a(n) for n=1..18.

Formula

a(n) = A006549(n) + 1. - Michel Marcus, Aug 25 2013

Mathematica

Join[{2}, Select[Range[0, 10^6], PrimePowerQ[#]&&PrimePowerQ[#-1]&]] (* James C. McMahon, Oct 05 2024 *)

Prog

(PARI) isokp(n) = (n==1) || isprime(n) || (ispower(n, , &k) && isprime(k));
isok(n) = isokp(n) && isokp(n-1); \\ Michel Marcus, Aug 25 2013

Crossrefs

Cf. A006549.

Sequence in context: A330400 A306044 A263581 * A295033 A152606 A057911

Adjacent sequences: A120427 A120428 A120429 * A120431 A120432 A120433

Keyword

nonn

Author

Greg Huber, Jul 13 2006

Status

approved