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 A164097 #23 Feb 24 2023 04:29:43
%S A164097 3,7,19,27,47,59,87,103,139,159,203,227,279,307,367,399,467,503,579,
%T A164097 619,703,747,839,887,987,1039,1147,1203,1319,1379,1503,1567,1699,1767,
%U A164097 1907,1979,2127,2203,2359,2439,2603,2687,2859,2947,3127,3219,3407,3503,3699
%N A164097 Numbers k such that 6*k + 7 is a perfect square.
%C A164097 The entries are prime, or divisible by 3, or divisible by prime of the form 3*m+1.
%H A164097 Vincenzo Librandi, <a href="/A164097/b164097.txt">Table of n, a(n) for n = 1..1000</a>
%H A164097 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A164097 From _R. J. Mathar_, Aug 26 2009: (Start)
%F A164097 a(n) = a(n-1) +2*a(n-2) -2*a(n-3) -a(n-4) +a(n-5).
%F A164097 G.f.: x*(-3-4*x-6*x^2+x^4)/((1+x)^2*(x-1)^3).
%F A164097 a(n) = 3*(2*n-1+2*n^2)/4 -(-1)^n*(1+2*n)/4 = A062717(n+1)-1. (End)
%F A164097 Sum_{n>=1} 1/a(n) = 1 + (tan((2+sqrt(7))*Pi/6) - cot((1+sqrt(7))*Pi/6))*Pi/(2*sqrt(7)). - _Amiram Eldar_, Feb 24 2023
%t A164097 Select[Range[4000], IntegerQ[Sqrt[6 # + 7 ]] &] (* or *) LinearRecurrence[{1, 2, -2, -1, 1}, {3, 7, 19, 27, 47}, 50] (* _Harvey P. Dale_, Apr 29 2011 *)
%o A164097 (Magma) [n: n in [1..4000] | IsSquare(6*n+7)]; // _Vincenzo Librandi_, Oct 12 2012
%Y A164097 Cf. A062717, A104777 (the squares 6*k+7).
%K A164097 nonn,easy
%O A164097 1,1
%A A164097 _Vincenzo Librandi_, Aug 10 2009
%E A164097 Edited by _R. J. Mathar_, Aug 26 2009