Index of 5^n within the sequence of the numbers of the form 5^i*7^j.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =11a(5) =16a(6) =21a(7) =27a(8) =34a(9) =42a(10) =51a(11) =61a(12) =71a(13) =82a(14) =94a(15) =107a(16) =121a(17) =136a(18) =151a(19) =167a(20) =184a(21) =202a(22) =221a(23) =241a(24) =261a(25) =282a(26) =304a(27) =327a(28) =351a(29) =375