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A240235 Least number k such that k*n^k - 1 is prime. a(n) = 0 if no such number exists. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) = 1 iff n-1 is prime.

a(145) is either 0 or > 275000. - Robert G. Wilson v, Jan 23 2017

LINKS

Robert G. Wilson v, Table of n, a(n) for n = 1..144

Steven Harvey, Generalized Woodall Primes

EXAMPLE

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.

PROG

(PARI) a(n)=k=1; while(!ispseudoprime(k*n^k-1), k++); return(k); n=1; while(n<100, print(a(n)); n+=1)

CROSSREFS

Cf. A066049, A239787, A281141.

Sequence in context: A291117 A293181 A229345 * A092742 A316564 A214742

Adjacent sequences:  A240232 A240233 A240234 * A240236 A240237 A240238

KEYWORD

nonn

AUTHOR

Derek Orr, Apr 02 2014

EXTENSIONS

a(23) and a(29) given using link. - Derek Orr, Aug 16 2014

STATUS

approved

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Last modified September 16 18:24 EDT 2019. Contains 327116 sequences. (Running on oeis4.)