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 A263469 #20 Jul 26 2024 08:00:22 %S A263469 0,2,3,4,5,6,7,15,17,21,42,57,99,312,372,15030 %N A263469 Numbers k such that k! + 2^k + 3 or k! + 2^k - 3 is prime. %C A263469 Both k! + 2^k + 3 and k! + 2^k - 3 are prime for k = 3 or 4. Are there any others? %C A263469 No more terms below 10^4. - _Charles R Greathouse IV_, Nov 17 2015 %e A263469 For k = 0, k! + 2^k + 3 = 0! + 2^0 + 3 = 5, which is prime. %e A263469 For k = 2, k! + 2^k - 3 = 2! + 2^2 - 3 = 3, which is prime. %t A263469 Select[Range[0, 10^3], Or[PrimeQ[#! + 2^# + 3], PrimeQ[#! + 2^# - 3]] &] (* _Michael De Vlieger_, Oct 20 2015 *) %o A263469 (PARI) for(n=0, 1e3, if(isprime(n!+2^n-3) || isprime(n!+2^n+3), print1(n", "))) %o A263469 (PARI) is(n)=my(N=n!+2^n); ispseudoprime(N-3) || ispseudoprime(N+3) \\ _Charles R Greathouse IV_, Nov 17 2015 %Y A263469 Cf. A007611, A261714, A263482. %K A263469 nonn,more %O A263469 1,2 %A A263469 _Altug Alkan_, Oct 19 2015 %E A263469 a(14)-a(15) from _Michael De Vlieger_, Oct 20 2015 %E A263469 a(16) from _Michael S. Branicky_, Jul 25 2024