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 A186948 #27 Sep 15 2024 20:24:39
%S A186948 1,1,5,21,73,233,717,2173,6545,19665,59029,177125,531417,1594297,
%T A186948 4782941,14348877,43046689,129140129,387420453,1162261429,3486784361,
%U A186948 10460353161,31381059565,94143178781,282429536433,847288609393,2541865828277,7625597484933,22876792454905,68630377364825
%N A186948 a(n) = 3^n - 2*n.
%C A186948 Binomial transform is A186947 and A186949.
%H A186948 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5,-7,3).
%F A186948 G.f.: (1 - 4*x + 7*x^2)/((1-x)^2*(1-3*x)).
%F A186948 a(n) = 3*a(n-1) + 2*(2*n - 3). - _Vincenzo Librandi_, Mar 13 2011
%F A186948 a(n) = 5*a(n-1) - 7*a(n-2) + 3*a(n-3); a(0)=1, a(1)=1, a(2)=5. - _Harvey P. Dale_, Nov 24 2011
%F A186948 E.g.f.: exp(x)*(exp(2*x) - 2*x). - _Elmo R. Oliveira_, Sep 15 2024
%t A186948 Table[3^n-2n,{n,0,30}] (* or *) LinearRecurrence[{5,-7,3},{1,1,5},30] (* _Harvey P. Dale_, Nov 24 2011 *)
%o A186948 (PARI) a(n)=3^n-2*n \\ _Charles R Greathouse IV_, Oct 16 2015
%Y A186948 Cf. A186947, A186949.
%K A186948 nonn,easy
%O A186948 0,3
%A A186948 _Paul Barry_, Mar 01 2011
%E A186948 a(26)-a(29) from _Elmo R. Oliveira_, Sep 15 2024