login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A071323 Alternating sum of all divisors of n; divisors nondecreasing, starting with 1. 3
1, -1, -2, 3, -4, -4, -6, -5, 7, -6, -10, -8, -12, -8, -12, 11, -16, -13, -18, -12, -16, -12, -22, -16, 21, -14, -20, -18, -28, -22, -30, -21, -24, -18, -32, 25, -36, -20, -28, -24, -40, -32, -42, -30, -36, -24, -46, -32, 43 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n)>0 iff n square (iff A000005(n) is even), a(A000290(n))>0;

for primes p: a(p) = 1 - p.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

Divisors of 20 are {1,2,4,5,10,20}, therefore a(20) = 1 - 2 + 4 - 5 + 10 - 20 = -12.

MATHEMATICA

Table[Total[Times@@@Partition[Riffle[Divisors[n], {1, -1}, {2, -1, 2

}], 2]], {n, 50}] (* Harvey P. Dale, Nov 05 2014 *)

CROSSREFS

Cf. A000203, A071321, A071324.

Sequence in context: A202650 A228286 A158973 * A071324 A321441 A063655

Adjacent sequences:  A071320 A071321 A071322 * A071324 A071325 A071326

KEYWORD

sign

AUTHOR

Reinhard Zumkeller, May 18 2002

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 22 17:18 EDT 2021. Contains 345388 sequences. (Running on oeis4.)