A175852 a(n) = the highest power of 5 with n decimal digits.

5, 25, 625, 3125, 78125, 390625, 9765625, 48828125, 244140625, 6103515625, 30517578125, 762939453125, 3814697265625, 95367431640625, 476837158203125, 2384185791015625, 59604644775390625, 298023223876953125

Offset: 1

Author

Zak Seidov, Sep 29 2010

Keywords

• base
• nonn

Comments

a(n) = 5^d(n), with

d(n) = {1, 2, 4, 5, 7, 8, 10, 11, 12, 14, 15, 17, 18, 20, 21, 22, 24, 25, 27, 28}.

If we redefine the sequence as a(n) = the highest power of 5 less than 10^n, then keyword "base" may be omitted.

d(n) = A066344(n). - Zak Seidov, Oct 01 2010

Programs

Mathematica

d[n_]=Floor@Log[5, 10^n]; a[n_]=5^d[n]