|
Search: id:A033993
|
|
|
| A033993 |
|
Numbers that are divisible by exactly four different primes. |
|
+0
15
|
|
| 210, 330, 390, 420, 462, 510, 546, 570, 630, 660, 690, 714, 770, 780, 798, 840, 858, 870, 910, 924, 930, 966, 990, 1020, 1050, 1092, 1110, 1122, 1140, 1155, 1170, 1190, 1218, 1230, 1254, 1260, 1290, 1302, 1320, 1326, 1330, 1365, 1380, 1386, 1410, 1428
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
For a(n) < 30030 = 2 * 3 * 5 * 7 * 11 * 13 this is identical to "numbers with a semiprime number of distinct prime factors." - Jonathan Vos Post (jvospost3(AT)gmail.com), Sep 21 2005
|
|
LINKS
|
T. D. Noe, Table of n, a(n) for n=1..1000
|
|
FORMULA
|
a(n) has exactly 4 distinct prime factors. omega(a(n)) = A001221(a(n)) = 4. - Jonathan Vos Post (jvospost3(AT)gmail.com), Sep 21 2005
|
|
EXAMPLE
|
The 4th primorial is the first: A002110[ 4 ]=210.
|
|
CROSSREFS
|
A000977, A007774, A000961, A002110, A033992, A051270.
Cf. A001221.
Sequence in context: A125011 A119427 A074159 this_sequence A046386 A046402 A147571
Adjacent sequences: A033990 A033991 A033992 this_sequence A033994 A033995 A033996
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu)
|
|
|
Search completed in 0.002 seconds
|
