A103069 - OEIS

%I #19 Jan 17 2019 13:44:07

%S 0,1,31,105,113,369,1359,6219,105571,150975

%N Numbers n such that 8*10^n + 3 is prime.

%C a(11) > 2*10^5. - _Robert Price_,  Aug 19 2015

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/8/80003.htm#prime">Prime numbers of the form 800...003</a>.

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

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.

%F a(n) = A101056(n-1) + 1, for n>1.

%e For n = 2 we have 8*10^1+3 = 8*10+3 = 83, which is prime.

%t Do[ If[ PrimeQ[ 8*10^n + 3], Print[ n ]], {n, 0, 10000}]

%o (PARI) is(n)=ispseudoprime(8*10^n+3) \\ _Charles R Greathouse IV_, Jun 12 2017

%Y Cf. A101056.

%K more,nonn

%O 1,3

%A _Robert G. Wilson v_, Jan 19 2005

%E Prepended a(1) = 0 by _Robert Price_, Aug 19 2015

%E a(9)-a(10) from _Robert Price_, Aug 19 2015