|
|
A033885
|
|
a(n) = 3*n - sum of divisors of n.
|
|
6
|
|
|
2, 3, 5, 5, 9, 6, 13, 9, 14, 12, 21, 8, 25, 18, 21, 17, 33, 15, 37, 18, 31, 30, 45, 12, 44, 36, 41, 28, 57, 18, 61, 33, 51, 48, 57, 17, 73, 54, 61, 30, 81, 30, 85, 48, 57, 66, 93, 20, 90, 57, 81, 58, 105, 42, 93, 48, 91, 84, 117, 12, 121, 90, 85, 65, 111, 54, 133, 78, 111, 66
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
The first zero term occurs at n=120. The first negative term is a(180) = -6. For any k, k*n - sigma(n) is negative for some n. See A023199. - T. D. Noe, Aug 07 2003
|
|
LINKS
|
Ivan Neretin, Table of n, a(n) for n = 1..10000
|
|
FORMULA
|
a(n) = A008585(n) - A000203(n). - Omar E. Pol, Sep 30 2017
|
|
EXAMPLE
|
For n=4, 3n=12, sum of divisors of n is 1+2+4=7, so a(4)=12-7=5.
|
|
MAPLE
|
with(numtheory): for n from 1 to 150 do printf(`%d, `, 3*n-sigma(n)) od:
|
|
MATHEMATICA
|
Table[3 n - DivisorSigma[1, n], {n, 70}] (* Ivan Neretin, Sep 30 2017 *)
|
|
PROG
|
(PARI) a(n)=3*n-sigma(n) \\ Charles R Greathouse IV, Mar 16 2016
|
|
CROSSREFS
|
Cf. A000203, A008585, A023199.
Sequence in context: A138181 A006447 A014237 * A053079 A326061 A158901
Adjacent sequences: A033882 A033883 A033884 * A033886 A033887 A033888
|
|
KEYWORD
|
sign
|
|
AUTHOR
|
N. J. A. Sloane
|
|
EXTENSIONS
|
More terms from James A. Sellers, Jun 01 2000
|
|
STATUS
|
approved
|
|
|
|