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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A079078 a(0) = 1, a(1) = 2; for n>1, a(n) = p(n)*a(n-2) where p(n) is the n-th prime. 7
1, 2, 3, 10, 21, 110, 273, 1870, 5187, 43010, 150423, 1333310, 5565651, 54665710, 239322993, 2569288370, 12684118629, 151588013830, 773731236369, 10156396926610, 54934917782199, 741416975642530, 4339858504793721 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Might be called the double primorial numbers and denoted by n##, by analogy with the double factorial numbers.

LINKS

Table of n, a(n) for n=0..22.

EXAMPLE

a(5)=110 because 2*5*11=110, the product of the first, third and fifth primes

PROG

(PARI) A079078(n)=prod(i=0, (n-1)\2, prime(n-2*i)) \\ - M. F. Hasler, May 04 2008

CROSSREFS

Cf. A006882, A002110.

Sequence in context: A161522 A120484 A113202 * A285794 A148056 A148057

Adjacent sequences:  A079075 A079076 A079077 * A079079 A079080 A079081

KEYWORD

nonn

AUTHOR

Michael Joseph Halm, Feb 02 2003

EXTENSIONS

Last term corrected by Jonathan Vos Post, Feb 09 2006

Edited and corrected by M. F. Hasler, May 06 2008

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified May 23 08:43 EDT 2017. Contains 286909 sequences.