This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A058934 #30 Dec 12 2021 20:07:54 %S A058934 0,1,3,13,45,105,159,297,1443,2977,3699,11709,12357,43165,121995 %N A058934 Numbers k such that 2*5^k + 1 is prime. %C A058934 a(n) is odd for n > 0. Next term > 17200. - _Julián Aguirre_, Apr 22 2011 %C A058934 a(16) > 2*10^5. - _Robert Price_, Mar 14 2015 %e A058934 a(3)=13 and 1 + 2*5^13 = 2441406251 is prime. %t A058934 Select[Range[0, 16000], PrimeQ[2*5^#+1]&] (* _Julián Aguirre_, Apr 22 2011 *) %o A058934 (Sage) %o A058934 [n for n in range(1500) if is_prime(2*5^n+1)] %o A058934 # _Julián Aguirre_, Apr 22 2011 %o A058934 (PARI) is(n)=ispseudoprime(2*5^n+1) \\ _Charles R Greathouse IV_, Jun 12 2017 %Y A058934 Cf. A003306 (2*3^n + 1 is prime), A120375 (2*5^n-1 is prime). %K A058934 nonn,more %O A058934 1,3 %A A058934 _Labos Elemer_, Jan 12 2001 %E A058934 Edited by _Joerg Arndt_, Apr 22 2011 %E A058934 Terms 1443,...,12357 from _Julián Aguirre_, Apr 22 2011 %E A058934 a(14)-a(15) from _Robert Price_, Mar 14 2015