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 A271328 #13 Apr 04 2016 16:00:40
%S A271328 1,5,10,17,28,37,50,65,82,106,122,145,170,197,228,257,294,325,362,406,
%T A271328 442,485,530,577,628,677,730,790,842,906,962,1025,1090,1161,1228,1297,
%U A271328 1376,1445,1522,1606,1682,1765,1850,1937,2028,2117,2210
%N A271328 a(n) = A269347(3*n)/3.
%C A271328 a(n) is equal to n^2 + 1 with predictable regularity; in particular, the values of n for which a(n) does not equal n^2 + 1 are exactly those values n for which 3n is divisible by A269347(3*m) for some m with 1 < m < n. This is in part because 1 + sum{i=1...n}(2i - 1) = n^2 + 1; when computing a(n), each term has this form except when the named condition holds.
%C A271328 For example, a(5) does not equal 5^2 + 1 because 3(5) is divisible by A269347(6).
%H A271328 Alec Jones, <a href="/A271328/b271328.txt">Table of n, a(n) for n = 1..10000</a>
%F A271328 a(n) = A269347(3*n)/3.
%o A271328 (PARI) lista(nn) = {nn *= 3; va = vector(nn); va[1] = 1; for (n=2, nn, va[n] = sum(k=1, n-1, k*((n % va[k])==0)); ); vector(#va\3, n, va[3*n]/3); } \\ _Michel Marcus_, Apr 04 2016
%Y A271328 Cf. A269347, A271326.
%K A271328 easy,nonn
%O A271328 1,2
%A A271328 _Alec Jones_, Apr 04 2016