|
| |
|
|
A066715
|
|
GCD of 2n+1 and sigma(2n+1).
|
|
5
| |
|
|
1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 7, 1, 5, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 13, 1, 1, 3, 1, 1, 1, 1, 1, 15, 1, 1, 3, 1, 5, 3, 1, 1, 9, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,8
|
|
|
COMMENTS
| If gcd(n, sigma(n))=1 then n is an odd perfect number. It seems however that gcd(n, sigma(n)) is always significantly less than n.
|
|
|
LINKS
| Harry J. Smith, Table of n, a(n) for n=0,...,1000
|
|
|
EXAMPLE
| a(5) = 1 as gcd(5,6) = 1. a(15) = gcd(15, sigma(15)) = gcd(15,(1+3+5+15)) = gcd(15,24) = 3
|
|
|
PROG
| (PARI) forstep (x=3, 2000, 2, write1("oddperfectgcd.txt", gcd(sigma(x), x), ", "))
(PARI) { for (n=0, 1000, write("b066715.txt", n, " ", gcd(2*n+1, sigma(2*n+1))) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Mar 19 2010]
|
|
|
CROSSREFS
| Sequence in context: A031244 A030576 A101874 * A082457 A031178 A091407
Adjacent sequences: A066712 A066713 A066714 * A066716 A066717 A066718
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Jon Perry (perry(AT)globalnet.co.uk), Jan 14 2002
|
| |
|
|
