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 A117794 #24 Mar 22 2021 05:47:30
%S A117794 0,6,66,120,276,378,630,780,1128,1326,1770,2016,2556,2850,3486,3828,
%T A117794 4560,4950,5778,6216,7140,7626,8646,9180,10296,10878,12090,12720,
%U A117794 14028,14706,16110,16836,18336,19110,20706,21528,23220,24090,25878,26796
%N A117794 Hexagonal numbers divisible by 6.
%C A117794 Intersection of A000384 and A008588. Their indices are given by A047238. - _Michel Marcus_, Feb 27 2014
%H A117794 Amiram Eldar, <a href="/A117794/b117794.txt">Table of n, a(n) for n = 1..10000</a>
%H A117794 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A117794 a(n) = a(n-1)+2*a(n-2)-2*a(n-3)-a(n-4)+a(n-5), with a(1)=0, a(2)=6, a(3)=66, a(4)=120, a(5)=276. - _Harvey P. Dale_, Aug 19 2011
%F A117794 a(n) = 3/2*(-1)^n(-4 n+(-1)^n*(6*n(2*n-5)+19)+5). - _Harvey P. Dale_, Aug 19 2011
%F A117794 G.f.: 6*x^2*(1+10*x+7*x^2+6*x^3)/((1-x)^3*(1+x)^2). - _Harvey P. Dale_, Aug 19 2011
%t A117794 Select[Table[n(2n-1),{n,0,250}],Divisible[#,6]&] (* or *) LinearRecurrence[ {1,2,-2,-1,1},{0,6,66,120,276},84] (* _Harvey P. Dale_, Aug 19 2011 *)
%o A117794 (PARI) isok(n) = ispolygonal(n, 6) && !(n % 6); \\ _Michel Marcus_, Feb 27 2014
%Y A117794 Cf. A000384, A008588, A047238.
%K A117794 nonn,easy
%O A117794 1,2
%A A117794 Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006