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 A176805 #28 Aug 19 2024 19:30:45 %S A176805 2,7,16,37,94,259,748,2209,6586,19711,59080,177181,531478,1594363, %T A176805 4783012,14348953,43046770,129140215,387420544,1162261525,3486784462, %U A176805 10460353267,31381059676,94143178897,282429536554,847288609519,2541865828408,7625597485069,22876792455046 %N A176805 a(n) = 3^n + 3*n + 1. %H A176805 Vincenzo Librandi, <a href="/A176805/b176805.txt">Table of n, a(n) for n = 0..200</a> %H A176805 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5,-7,3). %F A176805 a(n) = 3^n + 3n + 1 = A000244(n) + A008585(n) + 1 = A000244(n) + A016777(n). %F A176805 From _R. J. Mathar_, Apr 27 2010: (Start) %F A176805 a(n)= 5*a(n-1) - 7*a(n-2) + 3*a(n-3). %F A176805 G.f.: (1+x)*(5*x-2) / ( (3*x-1)*(x-1)^2 ). (End) %F A176805 E.g.f.: exp(x)*(1 + exp(2*x) + 3*x). - _Stefano Spezia_, Aug 19 2024 %e A176805 a(7) = (3^7) + (3*7) + 1 = 2209 = 47^2. %o A176805 (Magma) [3^n + 3*n + 1: n in [0..30]]; // _Vincenzo Librandi_, May 09 2011 %o A176805 (PARI) a(n)=3^n+3*n+1 \\ _Charles R Greathouse IV_, Oct 07 2015 %Y A176805 Cf. A000244, A008585, A016777, A176691. %K A176805 easy,nonn %O A176805 0,1 %A A176805 _Jonathan Vos Post_, Apr 26 2010 %E A176805 Corrected (1 replaced by 2, 2209 inserted) by _R. J. Mathar_, Apr 27 2010