A051818 Number of n-digit numbers with nonzero multiplicative digital root 7.
1, 3, 14, 86, 666, 6418, 64079, 597445, 5116146, 40671872, 304752986, 2187716324, 15395364971, 110611591118, 866239098731, 7907500662596
Offset: 1
References
- William Mayne, sci.math, Jun 15 1991
Formula
# { i : 10^(n-1) < i < 10^n and A051802(i)=7 }