|
Search: id:A067931
|
|
|
| A067931 |
|
Numbers n such that n divides the alternating sum sigma(1)-sigma(2)+sigma(3)-sigma(4)+...+((-1)^(n+1))sigma(n). |
|
+0
2
|
|
| 1, 2, 11, 19, 36, 45, 152, 377, 418, 3794, 4423, 14495, 31148, 42224, 49279, 120447, 1018376, 2605261
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
No further term below 10^7.
|
|
EXAMPLE
|
sigma(1)-sigma(2) = -2, which is divisible by 2, so 2 is a term of the sequence.
|
|
MATHEMATICA
|
s = 0; Do[s = s + (-1)^(i + 1) * DivisorSigma[1, i]; If[Mod[s, i] == 0, Print[i]], {i, 1, 10^5}]
|
|
PROGRAM
|
(PARI) {a067931(m)=local(s, n); s=0; for(n=1, m, if(n%2==0, s=s-sigma(n), s=s+sigma(n)); if(s%n==0, print1(n, ", ")))}
|
|
CROSSREFS
|
Cf. A000203, A068762.
Sequence in context: A152312 A154765 A163997 this_sequence A067660 A103200 A105076
Adjacent sequences: A067928 A067929 A067930 this_sequence A067932 A067933 A067934
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Feb 22 2002
|
|
EXTENSIONS
|
Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Feb 28 2002
|
|
|
Search completed in 0.002 seconds
|
