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 A306573 #23 May 15 2025 11:11:29 %S A306573 3,5,7,81,185,254,623,1087,2407,7862,8721,9353,13154,63003 %N A306573 Numbers k such that 11^(k+7) + 7^(k+5) + 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime. %C A306573 a(14) > 41000. - _Michael S. Branicky_, Mar 25 2023 %t A306573 ParallelMap[If[PrimeQ[11^(#+7) + 7^(#+5) + 5^(#+3) + 3^(#+2) + 2^(#+1) + 1], #, Nothing] &, Range@8000] %o A306573 (PARI) is(n) = ispseudoprime(11^(n+7) + 7^(n+5) + 5^(n+3) + 3^(n+2) + 2^(n+1) + 1) \\ _Felix Fröhlich_, Mar 06 2019 %K A306573 nonn,more,hard %O A306573 1,1 %A A306573 _Mikk Heidemaa_, Feb 24 2019 %E A306573 a(14) from _Michael S. Branicky_, May 15 2025