|
Search: id:A128269
|
|
|
| A128269 |
|
a(1)=1. a(n) = LCM((number of earlier terms which are coprime to n),(sum of the earlier terms which are coprime to n)). |
|
+0
2
|
|
| 1, 1, 2, 2, 12, 2, 60, 2, 30, 2, 570, 2, 4116, 2, 144, 2, 39600, 2, 747694, 2, 9720308, 2, 115638138, 2, 1261104380, 2, 3814717230, 2, 137331022698, 2, 2137994925180, 2, 8901006912, 2, 274682981784, 2, 46154014360092, 2, 29022598622, 2
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
For n > 2, a(n) is even since by induction the sum of coprimes is 1+1+some even numbers. Therefore a(n) = 2 for even n > 2 since only the 1's are coprime.
|
|
LINKS
|
H. v. Eitzen, Table of n, a(n) for n=1..10000
Leroy Quet, Home Page (listed in lieu of email address)
|
|
EXAMPLE
|
Among {a(1),a(2),...a(8)} the terms which are coprime to 9 are a(1)=a(2)=1 and a(3)=a(4)=a(6)=a(8)=2. There are 6 such terms. And the sum of these terms is 10. So a(8) = LCM(6,10) = 30.
|
|
CROSSREFS
|
Cf. A128268.
Sequence in context: A095215 A076976 A058044 this_sequence A109813 A086595 A013605
Adjacent sequences: A128266 A128267 A128268 this_sequence A128270 A128271 A128272
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Leroy Quet Feb 22 2007
|
|
EXTENSIONS
|
More terms copied from b-file by Hagen von Eitzen (math(AT)von-eitzen.de), Jun 24 2009
|
|
|
Search completed in 0.002 seconds
|
