A177956 Smallest k > 0 such that k^prime(n) - prime(n) is prime.

2, 2, 4, 60, 28, 2, 234, 2, 10, 186, 32, 8, 22, 6, 76, 330, 78, 62, 462, 88, 1416, 1440, 150, 40, 308, 144, 260, 42, 492, 2320, 132, 328, 838, 696, 736, 234, 56, 2786, 172, 382, 4872, 128, 4752, 7292, 826, 1856, 3960, 1124, 424, 612, 2052, 430, 1104, 280, 78, 286

Offset

1,1

Links

Table of n, a(n) for n=1..56.

Example

1^prime(1)-prime(1) = 1^2-2 = -1 is not prime, but 2^prime(2)-prime(2) = 2^2-2 = 2 is prime, hence a(1) = 2.
k^prime(4)-prime(4) is not prime for k < 60, but 60^prime(4)-prime(4) = 60^7-7 = 2799359999993 is prime, hence a(4) = 60.
a(19)^prime(19)-prime(19) = 462^67-67 has 179 digits.

Prog

(PARI) a177956(n) = {local(k=1, p=prime(n)); while(!isprime(k^p-p), k+=1); k}

Crossrefs

Cf. A000040, A084046, A084047, A177832.

Sequence in context: A257619 A075806 A295580 * A345758 A178981 A050923

Adjacent sequences: A177953 A177954 A177955 * A177957 A177958 A177959

Keyword

nonn

Author

Ulrich Krug (leuchtfeuer37(AT)gmx.de), May 16 2010

Extensions

Edited, keywords base, hard removed, PARI program and terms a(21) through a(56) added by the Associate Editors of the OEIS Klaus Brockhaus, May 23 2010

Extended by D. S. McNeil, May 23 2010

Status

approved