a(n) is the index of the smallest triangular number containing exactly n 4's.

A048359

a(n) is the index of the smallest triangular number containing exactly n 4's.

Terms

    a(0) =9a(1) =94a(2) =537a(3) =1043a(4) =29238a(5) =28790a(6) =94238a(7) =942703a(8) =2967970a(9) =45748113a(10) =170565790a(11) =939618480a(12) =2981759361a(13) =29814031731a(14) =94285146809a(15) =298802358238

External references