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A327661 Least number k > n - 2 such that k*n^k - 1 is prime. 2
3, 2, 2, 3, 8, 19, 18, 7, 10, 11, 252, 43, 563528, 98, 14, 167, 18, 28, 410, 44, 200, 140, 29028, 124, 68, 79, 2420, 47, 26850, 63, 2454, 140, 42, 164, 38, 62, 740, 67, 448, 51, 84, 135, 404882, 43, 84, 140, 140, 115, 710, 2390, 46640, 261, 60, 72, 2064, 414 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Different version of A240235. Some authors, like Caldwell (link), require that k + 2 > n before they use the term generalized Woodall for a prime of form k*n^k - 1.

LINKS

Jeppe Stig Nielsen, Table of n, a(n) for n = 1..144

Chris K. Caldwell, The Top Twenty: Generalized Woodall.

EXAMPLE

To find a(11), consider numbers k*11^k - 1 where k > 9. The first time it is prime, is for k = 252, so a(11) = 252.

PROG

(PARI) for(b=1, +oo, for(k=b-1, +oo, if(ispseudoprime(k*b^k-1), print1(k, ", "); next(2))))

CROSSREFS

Cf. A240235, A327660, A240234.

Sequence in context: A059942 A032450 A046460 * A117643 A141862 A237612

Adjacent sequences:  A327658 A327659 A327660 * A327662 A327663 A327664

KEYWORD

nonn,hard

AUTHOR

Jeppe Stig Nielsen, Sep 21 2019

STATUS

approved

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Last modified June 14 05:51 EDT 2021. Contains 345018 sequences. (Running on oeis4.)