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 A296031 #34 Apr 20 2025 12:30:18 %S A296031 5,11,15,17,27,51,57,71,117,2073,6251,13671,14217,14627,396128 %N A296031 Numbers k such that 2^(k-1) - k is prime. %C A296031 a(15) > 200000. - _Giovanni Resta_, May 13 2018 %F A296031 a(n) = A099439(n) + 1 = A063791(n) + 2. %e A296031 5 is in the sequence, because 2^4 - 5 = 11 is prime. %t A296031 Select[Range[6500], PrimeQ[2^(# - 1) - #] &] (* _Michael De Vlieger_, Apr 21 2018 *) %o A296031 (PARI) forstep(n=1, 10^6, 2, if(ispseudoprime(2^(n-1)-n),print1(n,", "))); \\ _Joerg Arndt_, Apr 15 2018 %Y A296031 Cf. A063791, A099439. %K A296031 nonn,more %O A296031 1,1 %A A296031 _Thomas Gajdek_, Dec 03 2017 %E A296031 Edited by _Joerg Arndt_, Apr 15 2018 %E A296031 a(15) from _Michael S. Branicky_, Apr 20 2025 using A099439