Index of smallest triangular number beginning with n.

Terms

a(0) =1a(1) =6a(2) =2a(3) =9a(4) =10a(5) =3a(6) =12a(7) =40a(8) =13a(9) =4a(10) =47a(11) =15a(12) =16a(13) =53a(14) =5a(15) =57a(16) =18a(17) =60a(18) =19a(19) =63a(20) =6a(21) =66a(22) =21a(23) =69a(24) =22a(25) =72a(26) =23a(27) =7a(28) =76a(29) =24