cp's OEIS Frontend

A117669 The n-th n-gonal number divisible by n.

%I A117669 #10 Jun 08 2024 17:04:33
%S A117669 1,4,15,64,210,630,1288,736,4959,9850,14421,6336,34840,57134,20805,
%T A117669 28288,141933,208818,253099,89200,107856,583462,680340,56304,1045675,
%U A117669 1367210,1553553,497056,2242164,687090,3155986,979456,1092861,5336674,1580845,1779408,7797898,9370838,2622789,756400
%N A117669 The n-th n-gonal number divisible by n.
%e A117669 The 5th number in the sequence must be the 5th pentagonal (5-gonal) number which can be divided by 5, namely 210.
%p A117669 A117669 := proc(n)
%p A117669     fdiv := 0 ;
%p A117669     for i from 1 do
%p A117669         if modp(A057145(n,i),n) = 0 then
%p A117669             fdiv := fdiv+1 ;
%p A117669             if fdiv = n then
%p A117669                 return A057145(n,i) ;
%p A117669             end if;
%p A117669         end if;
%p A117669     end do:
%p A117669 end proc:
%p A117669 seq(A117669(n),n=1..40) ; # _R. J. Mathar_, Nov 22 2022
%t A117669 Table[Select[PolygonalNumber[n,Range[2000]],Mod[#,n]==0&][[n]],{n,40}] (* _Harvey P. Dale_, Jun 08 2024 *)
%Y A117669 Cf. A057145.
%K A117669 nonn
%O A117669 1,2
%A A117669 Luc Stevens (lms022(AT)yahoo.com), Apr 11 2006
%E A117669 Offset and 2nd term corrected by _R. J. Mathar_, Nov 22 2022