A125845 n-digit numbers having n divisors each with a different number of digits.

1, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 121, 169, 289, 361, 529, 841, 961, 1111, 1133, 1177, 1199, 1243, 1313, 1331, 1339, 1391, 1397, 1417, 1441, 1469, 1507, 1529, 1639, 1651, 1661, 1703, 1717, 1727, 1751, 1781

Offset

1,2

Comments

A subsequence of A095862.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Sam Vandervelde, The Mandelbrot Competition, round 2, 2006-07, asked for the smallest composite number in this list.

Example

1 is the only one-digit number with only one factor. Two-digit primes are the only two-digit numbers in the list since they have a one-digit factor (1) and a two-digit factor (themselves). Three-digit squares of two-digit primes are the only three-digit numbers in the list, since only numbers of the form p^2 can have three factors.

Crossrefs

A125315 gives the smallest n-digit number of this form for each n.

Sequence in context: A226108 A273906 A095862 * A108871 A347819 A268031

Adjacent sequences: A125842 A125843 A125844 * A125846 A125847 A125848

Keyword

base,nonn

Author

Joshua Zucker, Dec 11 2006

Status

approved