A121154 a(n) = the n-th divisor of r(n)^n, where r(n) = (10^n-1)/9 the repunits and the positive divisors of r(n)^n are written in order from smallest to largest.

1, 11, 9, 121, 11111, 13, 21613201, 1111, 333, 4961, 219660193449998401, 49, 17530969, 562529, 333, 2057, 79066065031254967758669825213076144489, 91

Offset

1,2

Comments

Sequence continues: r(19)^18, 18491, 1933, 2101917, r(23)^22, 143, 458002801, 161051, 50653, 34001, ... - Charlie Neder, Mar 06 2019

Links

Charlie Neder, Table of n, a(n) for n = 1..37

Example

1, 11, 101, 121, 1111, 1331, 10201, 12221, 14641, 112211, 134431,... is the beginning of the sequence of divisors of 1111^4 and 121 is the 4th term of this sequence, so a(4) = 121.

Crossrefs

Cf. A121067.

Sequence in context: A335854 A220664 A038323 * A326587 A256078 A078200

Adjacent sequences: A121151 A121152 A121153 * A121155 A121156 A121157

Keyword

nonn

Author

Jason Earls, Aug 13 2006

Extensions

a(12)-a(18) from Charlie Neder, Mar 06 2019

Status

approved