A068538 Nonsquarefree repunits.

111111111, 111111111111111111, 1111111111111111111111, 111111111111111111111111111, 111111111111111111111111111111111111, 111111111111111111111111111111111111111111, 11111111111111111111111111111111111111111111, 111111111111111111111111111111111111111111111

Offset: 1

Author

Benoit Cloitre, Mar 22 2002

Keywords

• nonn

Comments

The number of digits of these repunits form the sequence A046412. - Michel Marcus, Nov 24 2013

Programs

PARI

lista(nn) = {for (n=1, nn, if (! issquarefree(r = sum(i=0, n, 10^i)), print1(r, ", ")););} \\ Michel Marcus, Nov 24 2013

Formula

a(n) = (10^A046412(n) - 1) / 9. - Max Alekseyev, Apr 29 2022