login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A209049 Smallest pentagonal number with n prime factors (counted with multiplicity). 1
1, 5, 22, 12, 210, 176, 1520, 1080, 8400, 55200, 273280, 43776, 2624832, 7173360, 71660160, 100659200, 34255872, 178962432, 3623854080, 17895751680, 5413478400, 43690752000, 927712542720, 733008101376, 1789570252800, 35917382287360, 50649120571392 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Pentagonal analogy of A075088.

LINKS

Table of n, a(n) for n=0..26.

MATHEMATICA

k = 1; t = Table[0, {50}]; While[k < 500000001, a = PrimeOmega[k] + PrimeOmega[3 k - 1] - 1; If[ t[[a + 1]] == 0, t[[a + 1]] = k; Print[{k, a}]]; k++]; # (3 # - 1)/2 & /@ t

CROSSREFS

Cf. A075088, A209048.

Sequence in context: A247937 A343840 A270406 * A217444 A063619 A229801

Adjacent sequences:  A209046 A209047 A209048 * A209050 A209051 A209052

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Mar 04 2012

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 September 28 09:32 EDT 2021. Contains 347714 sequences. (Running on oeis4.)