

A173101


Selfdescribing semiprimes.


1




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) = nth 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



