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 A175908 #18 Jul 12 2014 03:03:18
%S A175908 2,2,3,5,2,3,5,8,6,2,5,9,2,5,9,14,2,6,5,11,6,5,11,18,8,2,9,11,2,9,11,
%T A175908 20,6,2,11,21,2,5,15,20,2,6,5,17,12,11,17,30,14,8,9,11,2,9,17,26,6,2,
%U A175908 11,27,2,11,21,32,2,6,5,17,12,11,23,36,2,2,21,17,8,15,17,38
%N A175908 3*sum(k=1..n, floor(k^2/n)) - n^2.
%C A175908 According to the reference, a(p*q) = a(p) + a(q) - 2 whenever p and q are distinct primes with p congruent to q modulo 4.
%C A175908 The sequences of indices n where a(n)=2 is {1, 2, 5, 10, 13, 17, 26, ...}, which appears to be A020893 (squarefree sums of two squares). This has been confirmed for the first 500 terms. [_John W. Layman_, May 16 2011]
%H A175908 Walter Blumberg, <a href="http://www.jstor.org/stable/10.4169/000298910X515820">Problem 11529</a>, Amer. Math. Monthly, 117 (2010), 742.
%F A175908 a(n) = 3*A014817(n) - A000290(n). - _Wesley Ivan Hurt_, Jul 10 2014
%p A175908 A175908:=n->3*add(floor(k^2/n),k=1..n)-n^2: seq(A175908(n), n=1..60); # _Wesley Ivan Hurt_, Jul 10 2014
%t A175908 Table[3 Sum[Floor[k^2/n], {k, n}] - n^2, {n, 60}] (* _Wesley Ivan Hurt_, Jul 10 2014 *)
%o A175908 (PARI) a(n) = 3*sum(k=1, n, k^2\n) - n^2; \\ _Michel Marcus_, Jul 09 2014
%Y A175908 Cf. A020893.
%K A175908 nonn
%O A175908 1,1
%A A175908 _John W. Layman_, Oct 14 2010