Position of 5^n among the powers of primes (A000961).

Terms

a(0) =1a(1) =5a(2) =15a(3) =43a(4) =137a(5) =483a(6) =1881a(7) =7772a(8) =33292a(9) =146014a(10) =650688a(11) =2935909a(12) =13377899a(13) =61448617a(14) =284148766a(15) =1321470026a(16) =6175996065a(17) =28988110806a(18) =136575209239a(19) =645621236243