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 A275591 #61 Aug 05 2016 09:25:44
%S A275591 1,11,23,37,53,71,91,113,137,163,191,221,253,287,323,361,401,443,487,
%T A275591 533,581,631,683,737,793,851,911,973,1037,1103,1171,1241,1313,1387,
%U A275591 1463,1541,1621,1703,1787,1873,1961,2051,2143,2237,2333,2431,2531,2633,2737
%N A275591 a(n) = n^2 + 9*n + 1.
%C A275591 Also, nonnegative integers m such that 4*m + 77 is a square. The negative values of m are -7, -13, -17, -19.
%C A275591 The product of two consecutive terms belongs to the sequence. In fact: a(k)*a(k+1) = a(k*(k+1)+9*k+1).
%H A275591 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A275591 O.g.f.: (1 + 8*x - 7*x^2)/(1 - x)^3. - _Colin Barker_, Aug 03 2016
%F A275591 E.g.f.: (1 + 10*x + x^2)*exp(x).
%F A275591 a(n) = a(-n-9) = 3*a(n-1) - 3*a(n-2) + a(n-3). - _Colin Barker_, Aug 03 2016
%F A275591 a(n) = A048058(n-1) + A008592(n-1) for n>0.
%F A275591 a(n) = 1 + A028569(n). - _Omar E. Pol_, Aug 02 2016
%F A275591 a(n) + a(-n) = (n-1)^2 + (n+1)^2.
%F A275591 Sum_{i>=0} 1/a(i) = 9736/29393 + tan(sqrt(77)*Pi/2)*Pi/sqrt(77) = 1.301517...
%t A275591 Table[n^2 + 9 n + 1, {n, 0, 50}] (* _Bruno Berselli_, Aug 05 2016 *)
%o A275591 (PARI) a(n) = n^2 + 9*n + 1 \\ _Charles R Greathouse IV_, Aug 03 2016
%o A275591 (PARI) Vec((1+8*x-7*x^2)/(1-x)^3 + O(x^100)) \\ _Colin Barker_, Aug 04 2016
%Y A275591 Cf. A028569.
%Y A275591 Subsequence of A007775.
%K A275591 nonn,easy
%O A275591 0,2
%A A275591 _Miquel Cerda_, Aug 02 2016
%E A275591 Edited and extended by _Bruno Berselli_, Aug 05 2016