|
| |
|
|
A129087
|
|
Odd doubly abundant numbers (A125639).
|
|
0
| |
|
|
11025, 34155, 38745, 39585, 41895, 75735, 85995, 99225, 118755, 131355, 135135, 193725, 208845, 218025, 237195, 241395, 241605, 245385, 255645, 271215, 272745, 275625, 276885, 279279, 306495, 307125, 323505, 342225, 347985, 364455, 377685
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| This sequence contains the odd members of A125639, which (empirically) accounts for only about 0.08% of them.
|
|
|
FORMULA
| Odd numbers k, such that both k and s(k) (A001065) are abundant (A005101)
|
|
|
EXAMPLE
| The third odd number which is doubly abundant is 38745. Hence a(3)=38745
|
|
|
MATHEMATICA
| s[n_]:=DivisorSigma[1, n]-n; DoublyAbundantNumberQ[k_]:=If[s[k]>k && s[s[k]]>s[k], True, False]; Select[Range[500000], OddQ[ # ] && DoublyAbundantNumberQ[ # ] & ]
|
|
|
CROSSREFS
| Cf. A125639, A001065, A005101.
Sequence in context: A181319 A096930 A160711 * A156942 A164518 A198208
Adjacent sequences: A129084 A129085 A129086 * A129088 A129089 A129090
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| Ant King (mathstutoring(AT)ntlworld.com), Apr 02 2007
|
| |
|
|
