A181564 Semiprime convenient numbers.

4, 6, 9, 10, 15, 21, 22, 25, 33, 57, 58, 85, 93, 133, 177, 253

Offset

1,1

Comments

This is to semiprimes A001358 as A140768 is to primes A000040. Because Euler's "numerus idoneus" (idoneal, or suitable, or convenient numbers) are finite, this subset is finite. Conjecture: this list is complete (see Weinberger's result and comment by Jud McCranie in A140768).

Links

Table of n, a(n) for n=1..16.

Formula

A000926 INTERSECTION A001358.

Example

a(16) = A000926(50) = 253 = 11 * 23.

Crossrefs

Cf. A001358, A140768.

Sequence in context: A242664 A084662 A137167 * A119961 A122492 A178378

Adjacent sequences: A181561 A181562 A181563 * A181565 A181566 A181567

Keyword

nonn,fini

Author

Jonathan Vos Post, Jan 29 2011

Status

approved