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 A292313 #26 Oct 06 2017 01:56:24 %S A292313 75,300,507,675,867,1200,1875,2028,2523,2700,3468,3675,4107,4563,4800, %T A292313 5043,6075,7500,7803,8112,8427,9075,10092,10800,11163,12675,13872, %U A292313 14700,15987,16428,16875,18252,19200,20172,21675,22707,23763,24300,24843,27075,28227,30000,30603 %N A292313 Numbers that are the sum of three squares in arithmetic progression. %H A292313 Chai Wah Wu, <a href="/A292313/b292313.txt">Table of n, a(n) for n = 1..10000</a> %F A292313 Sequence is 3*(distinct elements in A198385). %F A292313 Numbers of the form 3*m^2 where 2*m^2 is in A004431. - _Chai Wah Wu_, Oct 05 2017 %e A292313 75 = 1^2 + 5^2 + 7^2 = 1 + 25 + 49, with 25 - 1 = 49 - 25 = 24. %e A292313 675 = 3^2 + 15^2 + 21^2 = 9 + 225 + 441, with 225 - 9 = 441 - 225 = 216. %o A292313 (PARI) t=4; k=3; while(t<=13000, i=k; e=0; v=t+i; while(i>1&&e==0, if(issquare(v), m=3*t; e=1; print1(m,", ")); i+=-2; v+=i); k+=2; t+=k) %Y A292313 Subsequence of A033428. %Y A292313 Cf. A000290, A000378, A004431, A134422, A292309, A292310, A292314, A292316. %K A292313 nonn %O A292313 1,1 %A A292313 _Antonio Roldán_, Sep 14 2017