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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A181564 Semiprime convenient numbers.

Original entry on oeis.org

4, 6, 9, 10, 15, 21, 22, 25, 33, 57, 58, 85, 93, 133, 177, 253
Offset: 1

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Author

Jonathan Vos Post, Jan 29 2011

Keywords

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).

Examples

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

Crossrefs

Cf. A001358, A140768.

Formula

A000926 INTERSECTION A001358.
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