A101824 -id:A101824 - cp's OEIS frontend

A100501 Numbers n such that 3*10^n+7 is prime.

1, 2, 5, 8, 24, 29, 84, 110, 129, 176, 593, 1137, 2675, 4992, 26904, 31572, 55077, 81021, 122274

Offset: 1

Julien Peter Benney (jpbenney(AT)ftml.net), Nov 23 2004

593 and 1137 both give primes. - Joao da Silva (zxawyh66(AT)yahoo.com), Sep 30 2005
a(19) > 10^5. - Robert Price, Jan 26 2015
a(20) > 2*10^5. - Robert Price, Jul 04 2015
Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019

			(3*10^5)+7 = (3*100000)+7 = 300000+7 = 300007, which is prime.

Makoto Kamada, Prime numbers of the form 300...007.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.

Cf. A096774, A101824.

Do[ If[ PrimeQ[ 3*10^n + 7], Print[ n ]], {n, 0, 20000}]

is(n)=ispseudoprime(3*10^n+7) \\ Charles R Greathouse IV, May 22 2017

a(n) = A101824(n) + 1.

a(12) from Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 26 2004
a(13)-a(14) from Hugo Pfoertner, Nov 29 2004. The next term is > 20000.
a(15) from Kamada data by Robert Price, Dec 12 2010
a(16)-a(18) from Kamada data by Robert Price, Jan 26 2015
a(19) from Robert Price, Jul 04 2015

cp's OEIS Frontend

A100501 Numbers n such that 3*10^n+7 is prime.

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