A289553 Numbers that are not the product of two distinct noncomposite numbers (A008578).

1, 4, 8, 9, 12, 16, 18, 20, 24, 25, 27, 28, 30, 32, 36, 40, 42, 44, 45, 48, 49, 50, 52, 54, 56, 60, 63, 64, 66, 68, 70, 72, 75, 76, 78, 80, 81, 84, 88, 90, 92, 96, 98, 99, 100, 102, 104, 105, 108, 110, 112, 114, 116, 117, 120, 121, 124, 125, 126, 128, 130, 132

Offset

1,2

Comments

Numbers k such that tau(k) = A000005(k) is not equal to 2*omega(k) = 2*A001221(k).

Links

Table of n, a(n) for n=1..62.

Example

Number 6 is not in the sequence because 6 = 2 * 3.

Prog

(Magma) [n: n in [1..1000] | NumberOfDivisors(n) ne 2*#PrimeDivisors(n)]

Crossrefs

Complement of A167171.

Cf. A246716 (with two distinct primes), A008578 (with two distinct nonprimes), A289555 (with two distinct composites).

Sequence in context: A020671 A171598 A259241 * A345212 A013929 A162966

Adjacent sequences: A289550 A289551 A289552 * A289554 A289555 A289556

Keyword

nonn

Author

Jaroslav Krizek, Jul 07 2017

Status

approved