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 A263718 #15 Nov 10 2015 10:42:08 %S A263718 1,3,4,15,24,58,168,234,324,375,3327,5788,8344,15039,59116,62620 %N A263718 n such that (1+2*7^n)/3 is prime. %C A263718 The numbers corresponding to a(11)-a(16) are only (extra-strong BPSW) probable primes. - _Charles R Greathouse IV_, Nov 10 2015 %t A263718 Select[Range@ 2000, PrimeQ[(1 + 2 7^#)/3] &] (* _Michael De Vlieger_, Nov 06 2015 *) %o A263718 (PARI) is(n)=ispseudoprime((1+2*7^n)/3) \\ _Charles R Greathouse IV_, Nov 06 2015 %K A263718 nonn %O A263718 1,2 %A A263718 _James R. Buddenhagen_, Oct 24 2015 %E A263718 a(11)-a(14) from _Charles R Greathouse IV_, Nov 06 2015 %E A263718 a(15)-a(16) from _Charles R Greathouse IV_, Nov 09 2015