A243218 Number of n-digit integers x such that x + A007954(x) has n digits, where A007954(x) is the product of decimal digits of x.
5, 63, 756, 8268, 86225, 880519, 8898517, 89471520, 897248572, 8985712192, 89925825853, 899614672173, 8997997446679, 89989593213308, 899945924502919, 8999718992342921, 89998539650321017, 899992410699128981, 8999960560129165187, 89999795045731606967
Offset: 1
Examples
For n=1, the five 1-digit integers 0,1,2,3,4 satisfy the condition, with results being respectively 0,2,4,6 and 8, hence a(1)=5.
Links
- Hiroaki Yamanouchi, Table of n, a(n) for n = 1..35
Programs
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PARI
DP(n)= my(d = digits(n)); prod(i=1, #d, d[i]); a(n) = {nb = 0; if (n==1, istart = 0, istart = 10^(n-1)); for (i=istart, 10^n-1, if (i + DP(i) < 10^n, nb++);); nb;}
Extensions
a(9)-a(17) from Hiroaki Yamanouchi, Sep 29 2014
a(18)-a(20) from Hiroaki Yamanouchi, Jan 08 2016