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