|
| |
|
|
A088827
|
|
Even numbers with odd abundance: even squares or two times squares. Sigma(n)-2n=odd means that sigma(n) is also odd.
|
|
4
|
|
|
|
2, 4, 8, 16, 18, 32, 36, 50, 64, 72, 98, 100, 128, 144, 162, 196, 200, 242, 256, 288, 324, 338, 392, 400, 450, 484, 512, 576, 578, 648, 676, 722, 784, 800, 882, 900, 968, 1024, 1058, 1152, 1156, 1250, 1296, 1352, 1444, 1458, 1568, 1600, 1682, 1764, 1800, 1922
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Odd numbers with odd abundance are in A016754. Odd numbers with even abundance are in A088828. Even numbers with even abundance are in A088829.
|
|
|
LINKS
|
Table of n, a(n) for n=1..52.
|
|
|
MATHEMATICA
|
Do[s=DivisorSigma[1, n]-2*n; If[OddQ[s]&&!OddQ[n], Print[{n, s}]], {n, 1, 1000}]
|
|
|
CROSSREFS
|
Cf. A016754, A088828-A088829.
Sequence in context: A127066 A154362 A072462 * A076057 A133809 A128700
Adjacent sequences: A088824 A088825 A088826 * A088828 A088829 A088830
|
|
|
KEYWORD
|
nonn,easy
|
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), Oct 28 2003
|
|
|
STATUS
|
approved
|
| |
|
|
