

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
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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)=127=5.


MAPLE

with(numtheory): for n from 1 to 150 do printf(`%d, `, 3*nsigma(n)) od:


MATHEMATICA

Table[3 n  DivisorSigma[1, n], {n, 70}] (* Ivan Neretin, Sep 30 2017 *)


PROG

(PARI) a(n)=3*nsigma(n) \\ Charles R Greathouse IV, Mar 16 2016


CROSSREFS

Cf. A000203, A008585, A023199.
Sequence in context: A138181 A006447 A014237 * A053079 A326061 A348203
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



