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 A240846 #19 Sep 08 2022 08:46:07
%S A240846 0,1,25,313,3769,45241,542905,6514873,78178489,938141881,11257702585,
%T A240846 135092431033,1621109172409,19453310068921,233439720827065,
%U A240846 2801276649924793,33615319799097529,403383837589170361,4840606051070044345,58087272612840532153
%N A240846 a(0)=0, a(1)=1, a(n) = a(n-1)*12 + 13.
%C A240846 a(n) is the total number of holes in a dodecaflake after n iterations.
%H A240846 G. C. Greubel, <a href="/A240846/b240846.txt">Table of n, a(n) for n = 0..900</a>
%H A240846 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (13,-12).
%F A240846 From _Colin Barker_, Apr 13 2014: (Start)
%F A240846 a(n) = (2^(2*n+1)*3^n - 13)/11 for n>0.
%F A240846 a(n) = 13*a(n-1) - 12*a(n-2) for n>2.
%F A240846 G.f.: x*(1+12*x) /((1-x)*(1-12*x)). (End).
%F A240846 E.g.f.: (11 - 13*exp(x) + 2*exp(12*x))/11. - _G. C. Greubel_, Feb 06 2020
%p A240846 A240846:=n->`if`(n=0, 0, (2^(1+2*n)*3^n-13)/11); seq(A240846(n), n=0..20); # _Wesley Ivan Hurt_, Apr 13 2014
%t A240846 Join[{0},NestList[12#+13&,1,20]] (* or *) LinearRecurrence[{13,-12},{0,1,25},30] (* _Harvey P. Dale_, Sep 08 2017 *)
%o A240846 (PARI) {a(n)=if(n<=0, 0, if(n<2, 1, a(n-1)*12+13))}
%o A240846 for(n=0, 20, print1(a(n),", "))
%o A240846 (Magma) [0] cat [(2^(2*n+1)*3^n - 13)/11: n in [1..20]]; // _G. C. Greubel_, Feb 06 2020
%o A240846 (Sage) [0]+[(2^(2*n+1)*3^n - 13)/11 for n in (1..20)] # _G. C. Greubel_, Feb 06 2020
%o A240846 (GAP) Concatenation([0], List([1..20], n-> (2^(2*n+1)*3^n - 13)/11 )); # _G. C. Greubel_, Feb 06 2020
%Y A240846 Cf. A240735.
%K A240846 nonn,easy
%O A240846 0,3
%A A240846 _Kival Ngaokrajang_, Apr 13 2014
%E A240846 Name changed by _Colin Barker_, Apr 13 2014