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 A253772 #38 Nov 12 2023 09:05:15 %S A253772 1,2,4,10,19,32,40,146,566,2054,9967,62639,87814,141092 %N A253772 Numbers k such that 4^k + 13 is prime. %C A253772 Numbers of the form 4^n+k (for n>0) are never primes when k is even (obviously) or when k == -1 (mod 6): in the last case, in fact, (3+1)^n + 6*h-1 is divisible by 3. - _Bruno Berselli_, Oct 06 2015 %F A253772 a(n) = A102634(n)/2. - _Elmo R. Oliveira_, Nov 12 2023 %t A253772 Select[Range[4000], PrimeQ[4^# + 13] &] %o A253772 (Magma) [n: n in [0..2000] | IsPrime(4^n+13)]; %o A253772 (PARI) is(n)=ispseudoprime(4^n+13) \\ _Charles R Greathouse IV_, Feb 17 2017 %Y A253772 Cf. A104067. %Y A253772 Cf. Numbers k such that 4^k + d is prime: A089437 (d=3), A217349 (d=7), A217350 (d=9), this sequence (d=13), A253773 (d=15), A253774 (d=19), A262345 (d=21), A204388 (d=25), A262969 (d=27), A262971 (d=31), A262972 (d=33). %K A253772 nonn,more %O A253772 1,2 %A A253772 _Vincenzo Librandi_, Jan 12 2015 %E A253772 a(11)-a(14) derived from A102634 by _Robert Price_, Sep 06 2015