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 A265486 #27 Aug 22 2025 17:38:03 %S A265486 3,6,15,19,36,75,80,118,199,336,360,520,1282,1810,2872,4870,14467, %T A265486 15102,22499,24675,45615,105648,116432 %N A265486 Numbers k such that 64^k - 8^k - 1 is prime. %C A265486 For k = 3, 6, 15, 19 the corresponding primes are 261631, 68719214591, 1237940039285345090527035391, 20769187434139310370006797241024511. %C A265486 3*a(n) belongs to A098845 (the terms from a(18) to a(23) are derived from that sequence). %e A265486 3 is in the sequence because 64^3 - 8^3 - 1 = 261631 is prime. %t A265486 Select[Range[1000], PrimeQ[64^# - 8^# - 1] &] %o A265486 (Magma) [n: n in [0..300] | IsPrime(64^n-8^n-1)]; %o A265486 (PARI) for(n=1, 1e3, if(ispseudoprime(64^n - 8^n - 1), print1(n, ", "))) \\ _Altug Alkan_, Dec 12 2015 %Y A265486 Cf. A098845, similar sequences listed in A265481. %K A265486 nonn,more %O A265486 1,1 %A A265486 _Vincenzo Librandi_, Dec 12 2015