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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
OFFSET
1,1
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
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