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

Author

Dan Hoey, Dec 09 1999

Keywords

• nonn
• base
• hard

References

• William Mayne, sci.math, Jun 15 1991

Crossrefs

Cf. A051802, A051806, A051824.

Formula

# { i : 10^(n-1) < i < 10^n and A051802(i)=4 }