|
Search: id:A060687
|
|
|
| A060687 |
|
Numbers n such that there exist exactly 2 Abelian groups of order n, i.e. A000688(n) = 2. |
|
+0
2
|
|
| 4, 9, 12, 18, 20, 25, 28, 44, 45, 49, 50, 52, 60, 63, 68, 75, 76, 84, 90, 92, 98, 99, 116, 117, 121, 124, 126, 132, 140, 147, 148, 150, 153, 156, 164, 169, 171, 172, 175, 188, 198, 204, 207, 212, 220, 228, 234, 236, 242, 244, 245, 260, 261, 268, 275, 276, 279
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
n belongs to this sequence iff exactly one prime in its factorization into prime powers has exponent 2 and all the other primes in the factorization have exponent 1, for example 60 = 2^2 * 3 * 5.
|
|
FORMULA
|
n such that A001222(n)-A001221(n) = 1
|
|
PROGRAM
|
(PARI) for(n=1, 279, if(bigomega(n)-omega(n)==1, print1(n, ", ")))
|
|
CROSSREFS
|
Cf. A000688.
Sequence in context: A081619 A038109 A067259 this_sequence A084789 A157650 A119640
Adjacent sequences: A060684 A060685 A060686 this_sequence A060688 A060689 A060690
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Ahmed Fares (ahmedfares(AT)my-deja.com), Apr 19 2001
|
|
EXTENSIONS
|
Corrected and extended by Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 05 2001
|
|
|
Search completed in 0.002 seconds
|
