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 A262787 #18 Mar 18 2025 15:25:05 %S A262787 41,68921,115856201,194754273881,327381934393961,550329031716248441, %T A262787 925103102315013629321,1555098314991537910888601, %U A262787 2614120267500775228203738281,4394336169668803158610484050361,7386879101213258109624223688656841,12417343769139486882278320020632149721 %N A262787 a(n) = 41^(2*n+1). %C A262787 41*a(n) is a square. %H A262787 G. C. Greubel, <a href="/A262787/b262787.txt">Table of n, a(n) for n = 0..250</a> %H A262787 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1681). %F A262787 G.f.: 41/(1 - 1681*x). %F A262787 a(n) = 1681*a(n-1). %p A262787 A262787:=n->41^(2*n+1): seq(A262787(n), n=0..20); # _Wesley Ivan Hurt_, Dec 26 2016 %t A262787 41^Range[1, 30, 2] %t A262787 NestList[1681#&,41,20] (* _Harvey P. Dale_, Mar 18 2025 *) %o A262787 (Magma) [41^(2*n+1): n in [0..15]]; %o A262787 (PARI) vector(20, n, n--; 41^(2*n+1)) \\ _Altug Alkan_, Oct 08 2015 %Y A262787 Second bisection of A009985 (powers of 41). %Y A262787 Cf. similar sequences listed in A262715. %K A262787 nonn,easy %O A262787 0,1 %A A262787 _Vincenzo Librandi_, Oct 08 2015