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%I #16 May 26 2018 11:16:38
%S 3,4,9,10,14,15,20,21,26,33,40,110,117,124,146,206,237,250,273,303,
%T 309,326,340,350,387,429,436,440,441,447,470,513,561,573,609,634,686,
%U 704,807,897,920,1004,1035,1054,1060,1071,1113,1124,1143,1156,1233,1239
%N Numbers x such that nextprime(x^2) - prevprime(x^2) = 4.
%C 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.
%F Solutions to {x; A007918(x^2)-A007917(x^2) = 4}.
%e n=3, n^2=9 is surrounded by closest primes: {7,[9],11};
%e n=10, n^2=100 is surrounded by {97,[100],101};
%t Select[Range[3,1500], NextPrime[#^2] == NextPrime[#^2, -1] + 4 &] (* _Giovanni Resta_, May 26 2018 *)
%o (PARI) isok(n) = nextprime(n^2) - precprime(n^2) == 4; \\ _Michel Marcus_, May 26 2018
%Y Cf. A090116, A090117, A090118, A090119, A007917, A007918, A000720, A000040, A053001, A007491, A000290.
%K nonn
%O 1,1
%A _Labos Elemer_, Jan 09 2004
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