|
| |
|
|
A070826
|
|
One half of product of first n primes A000040.
|
|
25
| |
|
|
1, 3, 15, 105, 1155, 15015, 255255, 4849845, 111546435, 3234846615, 100280245065, 3710369067405, 152125131763605, 6541380665835015, 307444891294245705, 16294579238595022365, 961380175077106319535
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
COMMENTS
| Identical with A002110(n)/2, n>=1.
a(n+1) is the least odd number with exactly n distinct prime divisors. - Labos E. (labos(AT)ana.sote.hu), Mar 24 2003
|
|
|
FORMULA
| a(n) = (1/2)*product(p(n), n=1..n) with p(n) := A000040(n).
|
|
|
MAPLE
| with (numtheory):a:=n->mul(ithprime(j), j=2..n):seq(a(n), n=1..17); [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Aug 24 2008]
|
|
|
MATHEMATICA
| Rest[ FoldList[ Times, 1, Prime[ Range[ 18]] ]]/2 (from Robert G. Wilson v Feb 17 2004)
FoldList[Times, 1, Prime[Range[2, 18]]] [From Zak Seidov (zakseidov(AT)yahoo.com), Jan 26 2009]
|
|
|
CROSSREFS
| Cf. A003266 (for Fibonacci), A070825 (for Lucas), A003046 (for Catalan).
Cf. also A091852.
Range of A196529.
Sequence in context: A001147 A000268 A118750 * A048599 A129731 A088109
Adjacent sequences: A070823 A070824 A070825 * A070827 A070828 A070829
|
|
|
KEYWORD
| nonn,easy
|
|
|
AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), May 10, 2002
|
|
|
EXTENSIONS
| Formula corrected by Gary Detlefs, Dec 07 2011.
|
| |
|
|
