Position of 7^n among 7-smooth numbers (A002473).

Terms

a(0) =1a(1) =7a(2) =30a(3) =87a(4) =202a(5) =403a(6) =726a(7) =1214a(8) =1911a(9) =2874a(10) =4158a(11) =5832a(12) =7968a(13) =10640a(14) =13933a(15) =17937a(16) =22747a(17) =28464a(18) =35195a(19) =43054a(20) =52162a(21) =62644a(22) =74630a(23) =88257a(24) =103671a(25) =121020a(26) =140462a(27) =162155a(28) =186267a(29) =212973