Index of smallest triangular number beginning with the n-th triangular number other than itself.

Terms

a(0) =4a(1) =8a(2) =11a(3) =14a(4) =17a(5) =20a(6) =75a(7) =85a(8) =95a(9) =105a(10) =36a(11) =39a(12) =135a(13) =145a(14) =155a(15) =165a(16) =553a(17) =58a(18) =616a(19) =648a(20) =680a(21) =711a(22) =743a(23) =77a(24) =806a(25) =838a(26) =869a(27) =901a(28) =933a(29) =96