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 A069224 #15 Sep 08 2022 08:45:05 %S A069224 1,2,3,5,6,7,8,9,12,13,14,15,20,30,32,35,36,37,38,39,44,47,49,56,60, %T A069224 63,65,66,75,80,84,90,93,96,98,102,104,110,113,117,119,125,129,130, %U A069224 133,139,140,145,146,149,150,153,155,159,162,167,170,179,180,183,184,192 %N A069224 Numbers n such that n^2 + n + A007918(n+2) is prime. %C A069224 Let K be the number of entries in the sequence less than or equal to M. Then the ratio K/M is nearly monotone decreasing. I do not know if the sequence converges, but if it does, it will be to a number less than 0.30. %H A069224 Robert Israel, <a href="/A069224/b069224.txt">Table of n, a(n) for n = 1..10000</a> %e A069224 35 is a term because 35^2 + 35 + 37 = 1297, which is prime. %p A069224 filter:= select(n -> isprime(n^2+n+nextprime(n+1)), [$1..200]); # _Robert Israel_, Aug 10 2018 %t A069224 Select[Range[200], PrimeQ[(NextPrime[# + 1] + #^2 + #)] &] (* _Vincenzo Librandi_, Aug 11 2018 *) %o A069224 (PARI) isok(n) = isprime(n^2 + n + nextprime(n+2)); \\ _Michel Marcus_, Aug 11 2018 %o A069224 (Magma)[n: n in [1..200] | IsPrime(n^2 + n + NextPrime(n+1))]; // _Vincenzo Librandi_, Aug 11 2018 %Y A069224 Cf. A007918. %K A069224 nonn %O A069224 1,2 %A A069224 Michael V. Scovetta (mike(AT)scovetta.com), Apr 12 2002 %E A069224 1 inserted, and definition corrected by _Robert Israel_, Aug 10 2018