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A204322 Numbers n such that 4*5^n + 1 is prime. 2
0, 2, 6, 18, 50, 290, 2582, 20462, 23870, 26342, 31938, 38122, 65034, 70130, 245538 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

All terms correspond to verified primes, that is, not merely probable primes. - Robert Price, Jan 16 2015

a(16) > 3*10^5. - Robert Price, Jan 16 2015

LINKS

Table of n, a(n) for n=1..15.

MATHEMATICA

Select[Range[0, 2000], PrimeQ[4*5^#+1]&]

PROG

(PARI) is(n)=ispseudoprime(4*5^n+1) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Sequence in context: A002900 A309087 A199770 * A196593 A248735 A219136

Adjacent sequences:  A204319 A204320 A204321 * A204323 A204324 A204325

KEYWORD

nonn

AUTHOR

José María Grau Ribas, Jan 14 2012

EXTENSIONS

a(8)-a(15) from Robert Price, Jan 16 2015

STATUS

approved

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Last modified August 21 08:25 EDT 2019. Contains 326162 sequences. (Running on oeis4.)