A289555 Numbers that are not the product of two distinct composite numbers (A002808).

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 57, 58, 59, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77

Offset

1,2

Links

Table of n, a(n) for n=1..67.

Example

Number 24 is not in the sequence because 24 = 4 * 6.

Prog

(Magma) [n: n in [1..1000] | (#PrimeDivisors(n) eq 1 and NumberOfDivisors(n) lt 6) or (#PrimeDivisors(n) eq 2 and NumberOfDivisors(n) lt 8) or (#PrimeDivisors(n) ge 3 and NumberOfDivisors(n) lt 12) ]

Crossrefs

Complement of A289554.

Cf. A246716 (with two distinct primes), A008578 (with two distinct nonprimes), A289553 (with two distinct noncomposites).

Sequence in context: A064598 A366187 A364354 * A354808 A048242 A272076

Adjacent sequences: A289552 A289553 A289554 * A289556 A289557 A289558

Keyword

nonn

Author

Jaroslav Krizek, Jul 07 2017

Status

approved