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 A089507 #17 Sep 08 2022 08:45:12 %S A089507 1,30,756,18360,441936,10614240,254788416,6115201920,146766525696, %T A089507 3522406694400,84537821131776,2028908069959680,48693795855814656, %U A089507 1168651113600245760,28047626804770062336,673143043784666480640 %N A089507 Second column of triangle A089504 and second column of array A078741 divided by 18. %C A089507 Convolution of A000400 (powers of 6) with A009968 (powers of 24). %H A089507 Vincenzo Librandi, <a href="/A089507/b089507.txt">Table of n, a(n) for n = 0..730</a> %H A089507 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (30,-144). %F A089507 G.f.: 1/((1-3*2*1*x)*(1-4*3*2*x)). %F A089507 a(n) = A089504(n+2, 2), n>=0. %F A089507 a(n) = (4*(4*3*2)^n - (3*2*1)^n)/3 = (2^n)*(2^(2*(n+1))-1)*3^(n-1). %F A089507 a(n) = 6^n*(4^(n+1)-1)/3. - _Vincenzo Librandi_, Oct 18 2017 %t A089507 CoefficientList[Series[1/((1-6x)(1-24x)),{x,0,20}],x] (* or *) LinearRecurrence[{30,-144},{1,30},20] (* _Harvey P. Dale_, Sep 25 2017 *) %o A089507 (Magma) [6^n*(4^(n+1)-1)/3: n in [0..15]]; // _Vincenzo Librandi_, Oct 18 2017 %Y A089507 Cf. A089505, A089513, A089514. %K A089507 nonn,easy %O A089507 0,2 %A A089507 _Wolfdieter Lang_, Dec 01 2003