A051827 Number of numbers below 10^n with nonzero multiplicative digital root 7.

1, 4, 18, 104, 770, 7188, 71267, 668712, 5784858, 46456730, 351209716, 2538926040, 17934291011, 128545882129, 994784980860, 8902285643456

Offset: 1

Author

Dan Hoey, Dec 09 1999

Keywords

• nonn
• base
• hard

Comments

Conjectured o(10^n)

References

• William Mayne, sci.math, Jun 15 1991

Crossrefs

Cf. A051802, A051809, A051818.

Formula

# { i : 10^(n-1) < i < 10^n and A051802(i)=7 }