A051815 Number of n-digit numbers with nonzero multiplicative digital root 4.
1, 12, 105, 780, 5452, 39979, 336081, 3263355, 34518027, 372779338, 3957184040, 40729856248, 406862880846, 3979167973684, 38556471560342, 374259579575061
Offset: 1
References
- William Mayne, sci.math, Jun 15 1991
Formula
# { i : 10^(n-1) < i < 10^n and A051802(i)=4 }