The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A289553 Numbers n that are not the product of two distinct noncomposite numbers (A008578). 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that tau(n) = A000005(n) is not equal to 2*omega(n) = 2*A001221(n). LINKS 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 * A013929 A162966 A190641 Adjacent sequences:  A289550 A289551 A289552 * A289554 A289555 A289556 KEYWORD nonn AUTHOR Jaroslav Krizek, Jul 07 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 28 23:19 EST 2020. Contains 332353 sequences. (Running on oeis4.)