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A051820
Number of n-digit numbers with nonzero multiplicative digital root 9.
1
1, 4, 25, 180, 1640, 17678, 213761, 2572363, 28717151, 295374892, 2863710220, 27059835840, 257084859669, 2498594395926, 24825380748687, 249116120158421
OFFSET
1,2
REFERENCES
William Mayne, sci.math, Jun 15 1991
FORMULA
# { i : 10^(n-1) < i < 10^n and A051802(i)=9 }
CROSSREFS
KEYWORD
nonn,base,hard
AUTHOR
Dan Hoey, Dec 09 1999
STATUS
approved