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A125845 n-digit numbers having n divisors each with a different number of digits. 2
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 (list; graph; refs; listen; history; text; internal format)
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 A268031 A167847

Adjacent sequences:  A125842 A125843 A125844 * A125846 A125847 A125848

KEYWORD

base,nonn

AUTHOR

Joshua Zucker, Dec 11 2006

STATUS

approved

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Last modified October 21 06:55 EDT 2019. Contains 328292 sequences. (Running on oeis4.)