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 A087426 #24 Feb 23 2025 11:20:10 %S A087426 0,3,27,216,1701,13365,104976,824499,6475707,50860872,399466485, %T A087426 3137450517,24641856288,193539651939,1520080160859,11938864580280, %U A087426 93769059774789,736471756750581,5784324272782128,45430672644283923 %N A087426 a(n) = S(n,4) where S(n,m) = sum(k=0,n,binomial(n,k)*Fibonacci(m*k)). %H A087426 M. Griffiths, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL15/Griffiths/griffiths20.html">Families of Sequences From a Class of Multinomial Sums</a>, J. Int. Seq. 15 (2012) # 12.1.8 %H A087426 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (9,-9). %F A087426 a(n) = 9*a(n-1)-9*a(n-2). %F A087426 a(n) = (1/sqrt(5))*(((9+3*sqrt(5))/2)^n-((9-3*sqrt(5))/2)^n). %F A087426 a(n) = 3^n*F(2n). - _Benoit Cloitre_, Sep 13 2005 %F A087426 G.f.: 3*x / (9*x^2-9*x+1). - _Colin Barker_, Jun 26 2013 %F A087426 E.g.f.: 2*exp(9*x/2)*sinh(3*sqrt(5)*x/2)/sqrt(5). - _Stefano Spezia_, Feb 23 2025 %Y A087426 Cf. A001906 (S(n,1)), A030191 (S(n,2)). %K A087426 nonn,easy %O A087426 0,2 %A A087426 _Benoit Cloitre_, Oct 23 2003