A246716 -id:A246716 - cp's OEIS frontend

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

Jaroslav Krizek, Jul 07 2017

nonn

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

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

Complement of A167171.

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

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

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

Original entry on oeis.org

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

Jaroslav Krizek, Jul 07 2017

nonn

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

Complement of A289554.

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

[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) ];

cp's OEIS Frontend

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

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