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 A158384 #4 Dec 11 2019 07:16:41 %S A158384 1,3,5,8,13,18,25,33,41,52,64,75,90,104,119,137,157,174,193,214,236, %T A158384 260,289,312,340,369,396,426,458,487,523,560,596,631,671,708,751,794, %U A158384 835,879,924,968,1019,1066,1116,1165,1218,1269,1322,1377,1430,1488,1551 %N A158384 Positions of Pell numbers in the sequence of Markoff numbers (A002559). %C A158384 Only the odd-indexed Pell numbers (A001653) appear in the Markoff sequence. The n-th term is about 0.5602*n^2. %Y A158384 Cf. A158381. %K A158384 nonn %O A158384 1,2 %A A158384 _T. D. Noe_, Mar 19 2009