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 A083231 #18 Aug 23 2024 23:20:52 %S A083231 1,3,21,87,489,2283,11901,58047,294609,1459923,7338981,36576807, %T A083231 183238329,915128763,4578832461,22884596367,114451679649,572172304803, %U A083231 2861119804341,14304824180727,71526445426569,357625253564043 %N A083231 a(n) = (3*5^n + (-3)^n)/4. %H A083231 Vincenzo Librandi, <a href="/A083231/b083231.txt">Table of n, a(n) for n = 0..300</a> %H A083231 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,15). %F A083231 a(n) = (3*5^n + (-3)^n)/4. %F A083231 G.f.: (1+x)/((1-5*x)*(1+3*x)). %F A083231 E.g.f.: (3*exp(5*x) + exp(-3*x))/4. %o A083231 (Magma) [(3*5^n+(-3)^n)/4: n in [0..25]]; // _Vincenzo Librandi_, Jun 29 2011 %Y A083231 Cf. A083232, A053524 (binomial transform, shifted). %K A083231 easy,nonn %O A083231 0,2 %A A083231 _Paul Barry_, Apr 23 2003