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 A109725 #11 Feb 15 2021 16:04:05
%S A109725 2,15,83,281,679,1367,2461,4005,6223,9017,12755,17281,22967,29597,
%T A109725 37793,47229,57993,70957,85343,101777,119469,141079,163313,188201,
%U A109725 216203,247203,280897,316551,355905,398825,445509,494953,549737,605711,665185,730353,801481
%N A109725 Divide primes in groups with 2n+1 elements and add together.
%C A109725 First difference of A109724.
%H A109725 Ray Chandler, <a href="/A109725/b109725.txt">Table of n, a(n) for n = 0..9999</a>
%F A109725 a(n) = A109724(n+1) - A109724(n) = A007504((n+1)^2) - A007504(n^2).
%t A109725 f[n_] := Sum[Prime[k], {k, n}]; Table[f[(n+1)^2] - f[n^2], {n, 0, 34}]
%t A109725 With[{nn=40},Total/@TakeList[Prime[Range[nn^2]],Range[1,2nn-1,2]]] (* Requires Mathematica version 11 or later *) (* _Harvey P. Dale_, Jan 05 2019 *)
%o A109725 (Python)
%o A109725 from sympy import prime
%o A109725 def a(n): return sum(prime(i) for i in range(n*n+1, (n+1)**2+1))
%o A109725 print([a(n) for n in range(37)]) # _Michael S. Branicky_, Feb 15 2021
%Y A109725 Cf. A007504, A109722-A109726.
%K A109725 easy,nonn
%O A109725 0,1
%A A109725 _Giovanni Teofilatto_, Aug 10 2005
%E A109725 Edited and extended by _Ray Chandler_, Aug 11 2005