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 A172001 #7 Jun 26 2022 16:16:11 %S A172001 34,136,146,178,194,205,221,305,306,377,386,410,466,482,505,514,544, %T A172001 545,562,584,674,689,706,712,745,776,793,802,820,850,866,884,890,898, %U A172001 905,1154,1186,1202,1205,1220,1224,1234,1282,1314,1345,1346,1394,1405,1469 %N A172001 Nonsquare positive integers n such that Pell equation y^2 - n*x^2 = -1 has rational solutions but the norm of fundamental unit of quadratic field Q(sqrt(n)) is 1. %C A172001 If the fundamental unit y0 + x0*sqrt(n) of Q(sqrt(n)) has norm -1, then (x0,y0) represents a rational solution to Pell equation y^2 - n*x^2 = -1. For n in this sequence, rational solutions exist but not delivered by the fundamental unit. %F A172001 A positive integer n is in this sequence iff its squarefree core A007913(n) belongs to A031398. %Y A172001 Set difference of A000415 and its subsequence A172000. %Y A172001 Set difference of A087643 and its subsequence A022544. %Y A172001 Squarefree terms form A031398. %Y A172001 Odd terms form A249052. %Y A172001 Cf. A031399, A137351. %K A172001 nonn %O A172001 1,1 %A A172001 _Max Alekseyev_, Jan 21 2010 %E A172001 Edited by _Max Alekseyev_, Mar 09 2010