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 A113478 #14 Feb 16 2025 08:32:59 %S A113478 0,1,4,11,28,64,173,438,1200,3325,9289,26494,76483,221530,645685, %T A113478 1895983,5593440,16578830,49347768,147402214,441641536,1326941536, %U A113478 3996900895,12066234206,36501753353 %N A113478 Number of cuban primes less than 10^n. %H A113478 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CubanPrime.html">Cuban Prime</a> %e A113478 7, 19, 37, 61, 127 are the first few cuban primes, so a(1)=1 and a(2)=4. %o A113478 (PARI) A113478(n)=sum(k=1,sqrt(10^n/3),isprime(3*k*(k+1)+1)) \\ _M. F. Hasler_, Nov 28 2007 %Y A113478 Cf. A002407, A002504. %K A113478 nonn,more %O A113478 0,3 %A A113478 _Eric W. Weisstein_, Jan 10 2006 %E A113478 a(15)-a(18) from _Donovan Johnson_, Feb 05 2010 %E A113478 a(19)-a(24) from _Hiroaki Yamanouchi_, Oct 08 2015