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 A253380 #23 Mar 22 2023 21:57:12 %S A253380 0,2,6,18,7238 %N A253380 Numbers k such that 17^k + 4 is prime. %C A253380 No further terms up to 10000. %C A253380 No further terms up to 37200. - _Michael S. Branicky_, Mar 22 2023 %e A253380 For k = 0: 17^0 + 4 = 5, which is prime, so 0 is a term of the sequence. %e A253380 For k = 2: 17^2 + 4 = 293, which is prime, so 2 is a term of the sequence. %t A253380 Select[Range@10^5, PrimeQ[17^# + 4] &] (* _Michael De Vlieger_, Jan 03 2015 *) %o A253380 (PARI) for(n=0, 1e5, if(ispseudoprime(17^n+4), print1(n, ", "))) %Y A253380 Corresponding sequences for k^n+4: A058958 (k=3), A124621 (k=5), A096305(k=7), A217384 (k=9), A137236 (k=13), A247166 (k=15), A243397 (k=19). %K A253380 nonn,more %O A253380 1,2 %A A253380 _Felix Fröhlich_, Dec 31 2014