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A177956 Smallest k > 0 such that k^prime(n) - prime(n) is prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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 * A178981 A050923 A326960

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

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Last modified December 14 22:42 EST 2019. Contains 329987 sequences. (Running on oeis4.)