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 A331698 #12 Jan 27 2020 07:56:47 %S A331698 1,1,3,1,5,4,6,7,6,6,9,10,13,12,13,12,14,15,19,18,18,15,21,21,25,20, %T A331698 26,17,23,27,28,31,30,31,35,33,32,37,34,33,35,36,34,43,39,42,45,33,45, %U A331698 45,48,45,53,42,46,55,49,51,56,53,60,52,60,60,63,64,61,53 %N A331698 a(n) = (1/2) * ((greatest prime < (n+1)^2) - (least prime > n^2)) for n >= 2. %H A331698 Hugo Pfoertner, <a href="/A331698/b331698.txt">Table of n, a(n) for n = 2..10000</a> %e A331698 a(2) = 1 because 7 is the greatest prime < 3^2 and 5 is the least prime > 2^2. (7-5)/2 = 1. %o A331698 (PARI) for(n=2, 69, print1((precprime((n+1)^2)-nextprime(n^2))/2, ", ")) %Y A331698 Cf. A007491, A053001, A132657. %K A331698 nonn %O A331698 2,3 %A A331698 _Hugo Pfoertner_, Jan 27 2020