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 A140676 #59 Jan 01 2023 03:19:55
%S A140676 0,7,20,39,64,95,132,175,224,279,340,407,480,559,644,735,832,935,1044,
%T A140676 1159,1280,1407,1540,1679,1824,1975,2132,2295,2464,2639,2820,3007,
%U A140676 3200,3399,3604,3815,4032,4255,4484,4719,4960,5207,5460,5719,5984,6255,6532,6815
%N A140676 a(n) = n*(3*n + 4).
%C A140676 The number of peers of a cell of an n^2 X n^2 sudoku is a(n-1). - _Neven Sajko_, Apr 20 2016
%C A140676 First differences are in A016921. - _Wesley Ivan Hurt_, Apr 21 2016
%H A140676 G. C. Greubel, <a href="/A140676/b140676.txt">Table of n, a(n) for n = 0..5000</a>
%H A140676 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A140676 a(n) = 3*n^2 + 4*n.
%F A140676 a(n) = 6*n + a(n-1) + 1 for n>0, a(0)=0. - _Vincenzo Librandi_, Aug 03 2010
%F A140676 O.g.f.: x*(7 - x)/(1 - x)^3. - _Arkadiusz Wesolowski_, Dec 24 2011
%F A140676 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>2. - _Harvey P. Dale_, May 04 2013
%F A140676 E.g.f.: x*(7 + 3*x)*exp(x). - _Ilya Gutkovskiy_, Apr 20 2016
%F A140676 a(n) = A000567(n+1) - 1. - _Neven Sajko_, Apr 20 2016
%F A140676 From _Amiram Eldar_, Feb 26 2022: (Start)
%F A140676 Sum_{n>=1} 1/a(n) = 15/16 - Pi/(8*sqrt(3)) - 3*log(3)/8.
%F A140676 Sum_{n>=1} (-1)^(n+1)/a(n) = 9/16 - Pi/(4*sqrt(3)). (End)
%p A140676 A140676:=n->n*(3*n+4): seq(A140676(n), n=0..100); # _Wesley Ivan Hurt_, Apr 21 2016
%t A140676 Table[n (3 n + 4), {n, 0, 50}] (* or *) LinearRecurrence[{3, -3, 1}, {0, 7, 20}, 50] (* _Harvey P. Dale_, May 04 2013 *)
%o A140676 (PARI) a(n)=n*(3*n+4) \\ _Charles R Greathouse IV_, Oct 07 2015
%o A140676 (Magma) [n*(3*n+4) : n in [0..80]]; // _Wesley Ivan Hurt_, Apr 21 2016
%Y A140676 Cf. A000567, A016921, A033428, A045944, A067707, A067725, A140677, A140678, A140679, A140680, A140681, A140689.
%K A140676 nonn,easy
%O A140676 0,2
%A A140676 _Omar E. Pol_, May 22 2008