A063570 Smallest positive power of 7 having n in its decimal representation.

4, 4, 4, 3, 2, 7, 5, 1, 5, 2, 13, 6, 12, 12, 19, 15, 5, 6, 19, 11, 12, 22, 14, 7, 4, 30, 11, 23, 10, 16, 14, 19, 11, 16, 3, 7, 9, 19, 12, 17, 4, 12, 27, 3, 18, 21, 32, 10, 8, 2, 15, 17, 10, 9, 7, 21, 15, 8, 21, 18, 9

Offset: 0

Author

Robert G. Wilson v, Aug 10 2001

Keywords

• base
• nonn

Links

• Chai Wah Wu, Table of n, a(n) for n = 0..10000

Crossrefs

Essentially the same as A062524.

Programs

Mathematica

a = {}; Do[k = 1; While[ StringPosition[ ToString[7^k], ToString[n] ] == {}, k++ ]; a = Append[a, k], {n, 0, 60} ]; a

Python

def A063570(n):
    m, k, s = 1, 7, str(n)
    while s not in str(k):
        m += 1
        k *= 7
    return m # Chai Wah Wu, Nov 14 2019