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 A128028 #15 Mar 11 2023 23:06:54 %S A128028 7,31,41,269,283,7333,8803 %N A128028 Numbers k such that (13^k - 3^k)/10 is prime. %C A128028 All terms are primes. %C A128028 No other terms exist < 100000. %t A128028 k=10; Select[ Prime[ Range[1,200] ], PrimeQ[ ((k+3)^# - 3^#)/k ]& ] %o A128028 (PARI) is(n)=isprime((13^n-3^n)/10) \\ _Charles R Greathouse IV_, Feb 17 2017 %Y A128028 Cf. A028491 = numbers n such that (3^n - 1)/2 is prime. Cf. A057468 = numbers n such that 3^n - 2^n is prime. Cf. A059801 = numbers n such that 4^n - 3^n is prime. Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime. Cf. A128024, A128025, A128026, A128027, A128029, A128030, A128031, A128032. %K A128028 hard,more,nonn %O A128028 1,1 %A A128028 _Alexander Adamchuk_, Feb 11 2007 %E A128028 One more term from _Farideh Firoozbakht_, Apr 03 2007 %E A128028 a(7)=8803 from _Robert Price_, Aug 12 2011