A182676 a(n) is the largest n-digit number with exactly 8 divisors, a(n) = 0 if no such number exists.
0, 88, 999, 9994, 99995, 999994, 9999994, 99999994, 999999998, 9999999995, 99999999998, 999999999998, 9999999999998, 99999999999998, 999999999999995, 9999999999999998, 99999999999999998, 999999999999999987, 9999999999999999995, 99999999999999999985, 999999999999999999995
Offset: 1
Links
- Amiram Eldar, Table of n, a(n) for n = 1..100
Programs
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Maple
with(numtheory): a:= proc(n) local k; if n<2 then 0 else for k from 10^n-1 while tau(k)<>8 by -1 do od; k fi end: seq(a(n), n=1..20); -
PARI
a(n)=forstep(k=10^n-1,10^(n-1),-1,numdiv(k)==8 & return(k)) \\ M. F. Hasler, Nov 27 2010
Formula
a(n) = max {10^(n-1) <= k < 10^n : A000005(k)=8} if set is nonempty, else a(n) = 0.
Extensions
Edited by Alois P. Heinz, Nov 27 2010
Given terms double-checked with given PARI code by M. F. Hasler, Nov 27 2010
a(20)-a(21) from Amiram Eldar, Apr 09 2024
Comments