login
A229663
Numbers n such that (40^n + 1)/41 is prime.
6
53, 67, 1217, 5867, 6143, 11681, 29959
OFFSET
1,1
COMMENTS
All terms are primes.
a(8) > 10^5.
LINKS
J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
H. Dubner and T. Granlund, Primes of the Form (b^n+1)/(b+1), J. Integer Sequences, 3 (2000), #P00.2.7.
Eric Weisstein's World of Mathematics, Repunit.
MATHEMATICA
Do[ p=Prime[n]; If[ PrimeQ[ (40^p + 1)/41 ], Print[p] ], {n, 1, 9592} ]
PROG
(PARI) is(n)=ispseudoprime((40^n+1)/41) \\ Charles R Greathouse IV, Feb 17 2017
KEYWORD
hard,more,nonn
AUTHOR
Robert Price, Sep 27 2013
STATUS
approved