A086064 In decimal representation: smallest k>1 such that n is a substring of n*k.

2, 10, 6, 10, 6, 3, 6, 10, 6, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 6, 10, 10, 10, 10, 5, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 6, 10, 10, 10, 10, 10, 10, 10, 10, 10, 3, 10, 10, 10, 10, 10, 10, 10, 10, 10, 6, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10

Offset: 0

Author

Reinhard Zumkeller, Aug 24 2003

Keywords

• nonn
• base

Comments

1 < a(n) <= 10; 4, 7 and 8 do not occur.

Crossrefs

Cf. A045537.

Programs

Python

def a(n):
    s = str(n)
    return next(k for k in range(2, 11) if s in str(n*k))
print([a(n) for n in range(71)]) # Michael S. Branicky, Feb 23 2025

Formula

a(n) = A087217(n)/n for n>0. - Reinhard Zumkeller, Aug 26 2003