login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A048692 Triangle read by rows in which row n contains first n numbers with exactly n distinct prime factors. 7
2, 6, 10, 30, 42, 60, 210, 330, 390, 420, 2310, 2730, 3570, 3990, 4290, 30030, 39270, 43890, 46410, 51870, 53130, 510510, 570570, 690690, 746130, 870870, 881790, 903210, 9699690, 11741730, 13123110, 14804790, 15825810, 16546530, 17160990 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..35.

EXAMPLE

2; 6 10; 30 42 60; 210 330 390 420; ...

MATHEMATICA

f[n_] := Flatten[Table[ # [[1]]] & /@ FactorInteger[n]]; (* for n=7 *) Take[ Select[ Range[10^7], Length[f[ # ]] == 7 & ], 7]

CROSSREFS

Cf. primorial numbers A002110.

Sequence in context: A032374 A074095 A079855 * A019095 A246349 A026117

Adjacent sequences:  A048689 A048690 A048691 * A048693 A048694 A048695

KEYWORD

nonn,tabl

AUTHOR

Amarnath Murthy, Aug 20 2002

EXTENSIONS

Edited, corrected and extended by Robert G. Wilson v, Aug 22 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 November 17 00:08 EST 2019. Contains 329209 sequences. (Running on oeis4.)