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 A087642 #5 Nov 02 2014 18:39:41 %S A087642 3,6,7,11,14,15,19,21,22,23,30,31,33,34,35,38,39,42,43,46,47,51,55,57, %T A087642 59,62,66,67,69,70,71,77,78,79,83,86,87,91,93,94,95,102,103,105,107, %U A087642 110,111,114,115,118,119,123,127,129,131,133,134,138,139,141,142,143,146 %N A087642 Sequence of squarefree n such that Q(sqrt(n)) has no element with a fully periodical continued fraction of period 1. %C A087642 Diophantine equation x^2 - n.y^2 + 4 = 0 has no solution (x,y) for a given squarefree n. Squarefree n not in the sequence A013946. Same sequence with square factors allowed is A087643. %e A087642 3 is in the sequence because no [k,k,k,k,...] is in Q(sqrt(3)) %e A087642 5 is not in the sequence since Q(sqrt(5)) contains [1,1,1,1,...] %Y A087642 Cf. A087643, A013946. %K A087642 easy,nonn %O A087642 3,1 %A A087642 _Thomas Baruchel_, Sep 16 2003