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 A146507 #22 Sep 11 2022 09:34:49
%S A146507 1,13,43,55,85,97,127,139,169,181,211,223,253,265,295,307,337,349,379,
%T A146507 391,421,433,463,475,505,517,547,559,589,601,631,643,673,685,715,727,
%U A146507 757,769,799,811,841,853,883,895,925,937,967,979
%N A146507 Numbers congruent to {1, 13} mod 42.
%C A146507 Positive integers k such that Hypergeometric[k/14,(14-k)/14,1/2,3/4] = 2*cos(2Pi/7).
%H A146507 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,-1).
%F A146507 a(2k-1) = 42*(k-1)+1, a(2k) = 42*(k-1)+13, where k>0.
%F A146507 G.f.: x*(1 + 12*x + 29*x^2)/((1 - x)^2*(1 + x)). - _Ilya Gutkovskiy_, Dec 06 2016
%F A146507 E.g.f.: 29 + ((42*x - 49)*exp(x) - 9*exp(-x))/2. - _David Lovler_, Sep 10 2022
%t A146507 Select[Range[1000],MemberQ[{1,13},Mod[#,42]]&] (* _Ray Chandler_, Dec 06 2016 *)
%t A146507 LinearRecurrence[{1,1,-1},{1,13,43},50] (* _Harvey P. Dale_, Apr 15 2020 *)
%Y A146507 Cf. A146509, A146510, A146511, A146512.
%K A146507 nonn
%O A146507 1,2
%A A146507 _Artur Jasinski_, Oct 30 2008
%E A146507 Description, formula and crossrefs corrected by _Ray Chandler_, Dec 06 2016