A096254 - OEIS

%I #26 Jan 17 2019 13:44:06

%S 1,2,3,8,18,20,31,42,103,175,181,531,706,1077,1177,1552,19737,32197,

%T 51508,58275,62233,90033

%N Numbers n such that 5*10^n + 3 is prime.

%C a(23) > 2*10^5. - _Robert Price_, Aug 03 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/5/50003.htm#prime">Prime numbers of the form 500...003</a>.

%H Sabin Tabirca and Kieran Reynolds, <a href="http://multimedia.ucc.ie/Staff/ST/articles/SNJ03_Tabirca1.ps">Lacunary Prime Numbers</a>.

%F a(n) = A101568(n) + 1.

%e 1, 2 and 3 are in the list because 53, 503 and 5003 are all prime.

%e 500000003 (5*10^8 + 3) is the next similar prime, so 8 is the next term in the sequence.

%t Do[ If[ PrimeQ[5*10^n + 3], Print[n]], {n, 10000}] (* _Robert G. Wilson v_, Aug 13 2004 *)

%o (PARI) is(n)=isprime(5*10^n+3) \\ _Charles R Greathouse IV_, Sep 27 2016

%Y Cf. A101568.

%K more,nonn

%O 1,2

%A _Carl R. White_, Aug 10 2004

%E a(12)-a(16) from _Robert G. Wilson v_, Aug 13 2004

%E a(17)-a(22) from Kamada data by _Robert Price_, Dec 09 2010