A077514 Largest n-digit squarefree number beginning with n.

29, 399, 4999, 59999, 699999, 7999999, 89999999, 999999998, 1099999999, 11999999999, 129999999999, 1399999999999, 14999999999999, 159999999999999, 1699999999999999, 17999999999999999, 189999999999999997

Offset

2,1

Comments

Let d = n - number of digits in n. Question: Is n*10^d -1 always a squarefree number?

If 9 divides n-1, then 9 divides n*10^d-1, so it is not squarefree. - Enrique Pérez Herrero, Apr 15 2015

Links

Table of n, a(n) for n=2..18.

Maple

a:= proc(n) local d, k;
     d:= ilog10(n)+1;
     for k from (n+1)*10^(n-d)-1 by -1 do
        if numtheory:-issqrfree(k) then return(k) fi
     od
end proc:
seq(a(n), n=2..50); # Robert Israel, Apr 17 2015

Crossrefs

Cf. A077513.

Sequence in context: A142327 A160298 A077508 * A210260 A010945 A022624

Adjacent sequences: A077511 A077512 A077513 * A077515 A077516 A077517

Keyword

base,nonn

Author

Amarnath Murthy, Nov 08 2002

Extensions

More terms from Sascha Kurz, Jan 04 2003

Status

approved