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 A233325 #24 Feb 10 2024 03:44:10
%S A233325 1,13,85,517,3109,18661,111973,671845,4031077,24186469,145118821,
%T A233325 870712933,5224277605,31345665637,188073993829,1128443962981,
%U A233325 6770663777893,40623982667365,243743896004197,1462463376025189,8774780256151141,52648681536906853
%N A233325 a(n) = (2*6^(n+1) - 7) / 5.
%C A233325 Sum of n-th row of triangle of powers of 6: 1; 6 1 6; 36 6 1 6 36; 216 36 6 1 6 36 216; ...
%H A233325 Vincenzo Librandi, <a href="/A233325/b233325.txt">Table of n, a(n) for n = 0..200</a>
%H A233325 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (7,-6).
%F A233325 G.f.: (1+6*x)/((1-x)*(1-6*x)).
%F A233325 a(n) = 7*a(n-1) - 6*a(n-2) for n>1, a(0)=1, a(1)=13.
%F A233325 a(n) = 6*a(n-1) + 7 for n>0, a(0)=1.
%F A233325 a(n) = A026567(2*n). - _Philippe Deléham_, Feb 24 2014
%e A233325 a(0) = 1;
%e A233325 a(1) = 6 + 1 + 6 = 13;
%e A233325 a(2) = 36 + 6 + 1 + 6 + 36 = 85;
%e A233325 a(3) = 216 + 36 + 6 + 1 + 6 + 36 + 216 = 517; etc.
%t A233325 Table[(2 6^(n + 1) - 7)/5, {n, 0, 20}] (* _Vincenzo Librandi_, Feb 25 2014 *)
%o A233325 (Magma) [(2*6^(n+1) - 7) / 5: n in [0..30]]; // _Vincenzo Librandi_, Feb 25 2014
%Y A233325 Cf. A026567.
%K A233325 nonn,easy
%O A233325 0,2
%A A233325 _Philippe Deléham_, Feb 23 2014