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 A117793 #20 Sep 08 2024 18:41:14
%S A117793 0,5,35,70,145,210,330,425,590,715,925,1080,1335,1520,1820,2035,2380,
%T A117793 2625,3015,3290,3725,4030,4510,4845,5370,5735,6305,6700,7315,7740,
%U A117793 8400,8855,9560,10045,10795,11310,12105,12650,13490,14065,14950,15555,16485
%N A117793 Pentagonal numbers divisible by 5.
%C A117793 Intersection of A008587 and A000326. Their indices are given by A047215. - _Michel Marcus_, Feb 27 2014
%H A117793 Robert Israel, <a href="/A117793/b117793.txt">Table of n, a(n) for n = 1..10000</a>
%F A117793 Empirical G.f.: x^2*(5+30*x+25*x^2+15*x^3)/(1-x)^3/(1+x)^2. - _Colin Barker_, Feb 14 2012
%F A117793 a(2*n+1) = 5*n*(15*n-1)/2, a(2*n+2) = 5*(5*n+2)*(3*n+1)/2. - _Robert Israel_, Jun 01 2014
%t A117793 Select[Table[PolygonalNumber[5, n], {n, 0, 100}], Divisible[#, 5] &] (* _Amiram Eldar_, Mar 22 2021 *)
%t A117793 Select[PolygonalNumber[5,Range[0,200]],Mod[#,5]==0&] (* _Harvey P. Dale_, Sep 08 2024 *)
%o A117793 (PARI) isok(n) = ispolygonal(n, 5) && !(n % 5); \\ _Michel Marcus_, Feb 27 2014
%Y A117793 Cf. A000326, A008587, A047215.
%K A117793 easy,nonn
%O A117793 1,2
%A A117793 Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006