Numbers that are both k-gonal and (k+1)-gonal for some k >= 3.

Terms

a(0) =1a(1) =36a(2) =1225a(3) =9801a(4) =40755a(5) =41616a(6) =121771a(7) =297045a(8) =631125a(9) =1212751a(10) =1413721a(11) =2158695a(12) =3617601a(13) =5773825a(14) =8851275a(15) =13117251a(16) =18886285a(17) =26523981a(18) =36450855a(19) =48024900a(20) =49146175a(21) =65151801a(22) =85076025a(23) =94109401a(24) =109597411a(25) =139468635a(26) =175520325a(27) =218664901a(28) =269900415a(29) =330314391