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 A090120 #24 Feb 25 2025 02:15:01
%S A090120 3,4,9,10,14,15,20,21,26,33,40,110,117,124,146,206,237,250,273,303,
%T A090120 309,326,340,350,387,429,436,440,441,447,470,513,561,573,609,634,686,
%U A090120 704,807,897,920,1004,1035,1054,1060,1071,1113,1124,1143,1156,1233,1239
%N A090120 Numbers k such that nextprime(k^2) - prevprime(k^2) = 4.
%C A090120 Note that the gap = 4 is partitioned either as 2+2 or as 3+1; 1+3 never occurs since n^2-1 is composite if n>2.
%H A090120 Amiram Eldar, <a href="/A090120/b090120.txt">Table of n, a(n) for n = 1..10000</a>
%F A090120 Solutions to {x; A007918(x^2)-A007917(x^2) = 4}.
%e A090120 k = 3 is a term since, k^2 = 9 is surrounded by the closest primes: {7,[9],11}.
%e A090120 k = 10 is a term since k^2 = 100 is surrounded by {97,[100],101}.
%t A090120 Select[Range[3,1500], NextPrime[#^2] == NextPrime[#^2, -1] + 4 &] (* _Giovanni Resta_, May 26 2018 *)
%o A090120 (PARI) isok(n) = nextprime(n^2) - precprime(n^2) == 4; \\ _Michel Marcus_, May 26 2018
%Y A090120 Cf. A090116, A090117, A090118, A090119, A007917, A007918, A000720, A000040, A053001, A007491, A000290.
%K A090120 nonn
%O A090120 1,1
%A A090120 _Labos Elemer_, Jan 09 2004