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!)
A114453 Number of 5-almost primes less than or equal to 10^n. 14
0, 0, 4, 76, 963, 11185, 124465, 1349779, 14371023, 150982388, 1570678136, 16218372618, 166497674684, 1701439985694, 17323079621014 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..14.

EXAMPLE

There are 4 five-almost primes up to 100: 32,48,72&80.

MATHEMATICA

FiveAlmostPrimePi[n_] := Sum[ PrimePi[n/(Prime@i*Prime@j*Prime@k*Prime@l)] - l + 1, {i, PrimePi[n^(1/5)]}, {j, i, PrimePi[(n/Prime@i)^(1/4)]}, {k, j, PrimePi[(n/(Prime@i*Prime@j))^(1/3)]}, {l, k, PrimePi[(n/(Prime@i*Prime@j*Prime@k))^(1/2)]}]; Table[ FiveAlmostPrimePi[10^n], {n, 0, 12}]

CROSSREFS

Cf. A006880, A066265, A109251, A014613, A116382.

Sequence in context: A045996 A190395 A240281 * A093184 A214814 A144210

Adjacent sequences:  A114450 A114451 A114452 * A114454 A114455 A114456

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Feb 07 2006

EXTENSIONS

a(13) and a(14) from Robert G. Wilson v, Jan 07 2007

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 29 07:08 EDT 2020. Contains 337425 sequences. (Running on oeis4.)