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A173101 Self-describing semiprimes. 1
22, 10183133, 10183331, 10213223 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This is to A001358 as A108810 is to A000040.

LINKS

Table of n, a(n) for n=1..4.

FORMULA

{A109776 INTERSECTION A001358}. a(n) = n-th integer k such that OMEGA(k)=2 where OMEGA(n) is the sum of the exponents in the prime decomposition of k, and reading the number (in base 10) in successive pairs of digits gives a (possibly redundant) description of the number.

EXAMPLE

a(1) = 22 because "22" does indeed consist of "two 2's" and 22 = 2 * 11 is semiprime. a(4) = 10213223 because 10213223 consists of one "0", two 1's, three 2's, and two 3's; and 10213223 = 41 * 249103 is semiprime.

CROSSREFS

Cf. A001358, A108810, A109776.

Sequence in context: A267492 A013816 A104789 * A047841 A267498 A267497

Adjacent sequences:  A173098 A173099 A173100 * A173102 A173103 A173104

KEYWORD

base,more,nonn

AUTHOR

Jonathan Vos Post, Feb 09 2010

STATUS

approved

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Last modified October 21 17:10 EDT 2018. Contains 316427 sequences. (Running on oeis4.)