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 A081666 #11 Aug 06 2022 12:56:19
%S A081666 1,4,16,62,233,855,3083,10978,38746,135924,474955,1655789,5766389,
%T A081666 20080608,69976772,244166410,853410637,2988825507,10490538559,
%U A081666 36905911166,130139760590,459970519296,1629395348591,5784362027257
%N A081666 n*3^(n-1)+A081567(n).
%C A081666 Binomial transform of A081663.
%H A081666 Harvey P. Dale, <a href="/A081666/b081666.txt">Table of n, a(n) for n = 0..1000</a>
%H A081666 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (11,-44,75,-45).
%F A081666 a(n)=A027471(n-1)+A081567(n) G.f.: (1-7x+16x^2-13x^3)/((3x - 1)^2(5x^2-5x+1))
%t A081666 LinearRecurrence[{11,-44,75,-45},{1,4,16,62},30] (* _Harvey P. Dale_, Aug 06 2022 *)
%Y A081666 Cf. A000045.
%K A081666 easy,nonn
%O A081666 0,2
%A A081666 _Paul Barry_, Mar 26 2003