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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A273289 Least prime not less than the median of all prime divisors of n counted with multiplicity. 4
2, 3, 2, 5, 3, 7, 2, 3, 5, 11, 2, 13, 5, 5, 2, 17, 3, 19, 2, 5, 7, 23, 2, 5, 11, 3, 2, 29, 3, 31, 2, 7, 11, 7, 3, 37, 11, 11, 2, 41, 3, 43, 2, 3, 13, 47, 2, 7, 5, 11, 2, 53, 3, 11, 2, 11, 17, 59, 3, 61, 17, 3, 2, 11, 3, 67, 2, 13, 5, 71, 2, 73, 23, 5, 2, 11, 3, 79, 2, 3, 23 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

A273288(n)<= a(n)<= A006530<= n and a(n) = n iff n is prime.

LINKS

Giuseppe Coppoletta, Table of n, a(n) for n = 2..10000

EXAMPLE

a(76) = 2 because the median of its prime factors [2, 2, 19] is the central value 2 (and it is prime).

a(308) = 5 because the median of [2, 2, 7, 11] is commonly defined as the mean of the central values (2+7)/2 = 4.5 and the next prime is 5.

MATHEMATICA

Table[If[PrimeQ@ #, #, NextPrime@ #] &@ Median@ Flatten@ Apply[Table[#1, {#2}] &, FactorInteger@ n, 1], {n, 2, 82}] (* Michael De Vlieger, May 27 2016 *)

PROG

(Sage) r = lambda n: [f[0] for f in factor(n) for _ in range(f[1])]; [next_prime(ceil(median(r(n)))-1) for n in (2..100)]

CROSSREFS

Cf. A273283, A273285, A273288, A273291, A079870, A006530.

Sequence in context: A086287 A253236 A286516 * A090662 A088387 A197861

Adjacent sequences:  A273286 A273287 A273288 * A273290 A273291 A273292

KEYWORD

nonn

AUTHOR

Giuseppe Coppoletta, May 25 2016

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 August 26 00:35 EDT 2019. Contains 326324 sequences. (Running on oeis4.)