A240235 Least number k such that k*n^k - 1 is prime. a(n) = 0 if no such number exists.
3, 2, 1, 1, 8, 1, 2, 1, 10, 2, 2, 1, 2, 1, 2, 167, 2, 1, 12, 1, 2, 2, 29028, 1, 2, 3, 10, 2, 26850, 1, 8, 1, 42, 2, 6, 2, 24, 1, 2, 3, 2, 1, 2, 1, 2, 2, 140, 1, 2, 2, 22, 2, 8, 1, 2064, 2, 468, 6, 2, 1, 362, 1, 2, 2, 6, 3, 26, 1, 2, 3, 20, 1, 2, 1, 28, 2, 38, 5, 3024, 1, 2, 81, 858, 1
Offset: 1
Keywords
Examples
1*1^1 - 1 = 0 is not prime. 2*1^2 - 1 = 1 is not prime. 3*1^3 - 1 = 2 is prime. Thus, a(1) = 3.
Links
- Robert G. Wilson v, Table of n, a(n) for n = 1..144
- Steven Harvey, Generalized Woodall Primes
Programs
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PARI
a(n)=k=1;while(!ispseudoprime(k*n^k-1),k++);return(k); n=1;while(n<100,print(a(n));n+=1)
Extensions
a(23) and a(29) given using link. - Derek Orr, Aug 16 2014
Comments