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A056805
Numbers k such that 6*10^k+1 is prime.
10
0, 1, 2, 8, 9, 15, 20, 26, 38, 45, 65, 112, 244, 303, 393, 560, 839, 1009, 1019, 1173, 1334, 2236, 2629, 4426, 8848, 20812, 37744, 72926, 86287, 231617, 281969, 488852, 522127, 655642, 758068, 879313, 1380098
OFFSET
1,3
COMMENTS
From the Kamada data, Edward Trice reports that 231617 and 522127 are in this sequence. But these may not be the next ones. There are no others less than 2*10^5, however. - Robert Price, Jul 09 2015
LINKS
FORMULA
a(n) = A101517(n-1) + 1.
EXAMPLE
For k=2 => (6*10^2+1)=601, which is prime.
MATHEMATICA
Do[ If[ PrimeQ[ 6*10^n + 1], Print[ n ]], {n, 0, 10000}]
PROG
(PARI) is(n)=isprime(6*10^n+1) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
Sequence in context: A032928 A287564 A158458 * A226825 A367984 A046679
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Aug 22 2000
EXTENSIONS
a(22)-a(25) from Hugo Pfoertner, Feb 11 2004
a(26)=20812 from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 27 2007
a(27)=37744 from Jason Earls, Mar 07 2008
a(28)-a(29) from Kamada data by Robert Price, Dec 09 2010
a(30)-a(36) from Kamada data by Tyler Busby, Apr 15 2024
STATUS
approved