|
Search: id:A067023
|
|
|
| A067023 |
|
Sigma-crowded numbers: n such that d(n)/sigma[n] is larger than d(m)/sigma[m] for all m>n. |
|
+0
3
|
|
| 1, 2, 3, 4, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 30, 36, 40, 42, 48, 60, 72, 80, 84, 90, 96, 120, 126, 144, 168, 180, 210, 240, 252, 280, 288, 300, 360, 420, 432, 480, 504, 540, 560, 600, 630, 720, 840, 900, 1008, 1080, 1260
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
Since d(m)<2sqrt(m)<2sigma[m], we need only test values of m <(2sigma[n]/d(n))^2.
|
|
MATHEMATICA
|
crowded[n_] := Module[{}, stop=(2/(dovern=DivisorSigma[0, n]/DivisorSigma[1, n]))^2; For[m=n+1, m<stop, m++, If[DivisorSigma[0, m]/DivisorSigma[1, m] >=dovern, Return[False]]]; True]; Select[Range[1, 13000], crowded]
|
|
CROSSREFS
|
An analogue of A066523. Cf. A002182, A000005, A000203, A004394, A034884, A056758.
Sequence in context: A160719 A085451 A064150 this_sequence A002183 A060306 A158614
Adjacent sequences: A067020 A067021 A067022 this_sequence A067024 A067025 A067026
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), Jan 09 2002
|
|
|
Search completed in 0.002 seconds
|
