A173101 - OEIS

A173101

Self-describing semiprimes.

22, 10183133, 10183331, 10213223, 10313317, 10322123, 10331831, 10331931, 10333117, 12183133, 12183331, 12193331, 12311033, 12311633, 12311833, 12313318, 12331031, 12333115, 12333119, 14103331, 14153331, 14163133, 14173133, 14183133, 14193331, 14311533, 14311633

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OFFSET

1,1

COMMENTS

This is to A001358 as A108810 is to A000040.

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..10000

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

nonn,base,fini,less

AUTHOR

Jonathan Vos Post, Feb 09 2010

EXTENSIONS

More terms from Giovanni Resta, Aug 14 2019

STATUS

approved