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 A230060 #11 Sep 15 2024 14:03:56 %S A230060 1,3,5,6,7,9,11,15,18,20,28,30,35,42,45,54,60,63,66,77,78,88,90,102, %T A230060 105,114,117,126,130,138,150,162,165,174,175,186,198,204,210,221,222, %U A230060 234,245,246,247,258,264,266,270,282,294,306,315,318,330,342,351,354,366,368,378,385,390 %N A230060 Numbers k such that the distance from k^2 to the smallest triangular number >= k^2 is itself triangular. %o A230060 (PARI) is(n)=my(t=floor((sqrt(8*n^2)-1)/2)+1);t=t*(t+1)/2-n^2; my(tt=floor((sqrt(8*t)-1)/2)+1);(tt*(tt+1)/2==t) %Y A230060 Cf. A230038. %K A230060 nonn %O A230060 1,2 %A A230060 _Ralf Stephan_, Oct 08 2013