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A071381
Numbers n such that (28^n+1)/29 is a prime.
16
3, 19, 373, 419, 491, 1031, 83497, 223381
OFFSET
1,1
COMMENTS
(28^1031+1)/29, a 1491-digit number, has now been certified prime with Primo.
a(8) > 10^5. - Robert Price, Jul 10 2013
LINKS
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
PROG
(PARI) isok(n) = (denominator(p=(28^n+1)/29)==1) && isprime(p); \\ Michel Marcus, Oct 29 2017
CROSSREFS
Sequence in context: A357956 A229832 A219270 * A195639 A195640 A195641
KEYWORD
nonn,more
AUTHOR
Rick L. Shepherd, May 22 2002
EXTENSIONS
a(7) from Robert Price, Jul 10 2013
a(8)=223381 corresponds to a probable prime discovered by Paul Bourdelais, Dec 23 2020
STATUS
approved