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

 

Logo

Annual Appeal: Please make a donation to keep the OEIS running. In 2018 we replaced the server with a faster one, added 20000 new sequences, and reached 7000 citations (often saying "discovered thanks to the OEIS").
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A067620 a(n) = p^e, where p and e are the rounded means of the prime factors p_i and the exponents e_i, respectively, in the factorization n = p_1^e_1 * ... * p_r^e_r of n into distinct primes p_i. Each mean is rounded to the nearest integer, rounding up if there's a choice. 0
2, 3, 4, 5, 3, 7, 8, 9, 4, 11, 9, 13, 5, 4, 16, 17, 9, 19, 16, 5, 7, 23, 9, 25, 8, 27, 25, 29, 3, 31, 32, 7, 10, 6, 9, 37, 11, 8, 16, 41, 4, 43, 49, 16, 13, 47, 27, 49, 16, 10, 64, 53, 9, 8, 25, 11, 16, 59, 3, 61, 17, 25, 64, 9, 5, 67, 100, 13, 5, 71, 27, 73, 20, 16, 121, 9, 6, 79 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..79.

EXAMPLE

24 = 2^3 * 3^1. The prime factors have mean (2+3)/2 = 2 1/2, which rounds up to 3. The exponents have mean (3+1)/2 = 2. So a(24) = 3^2 = 9.

MAPLE

with(numtheory): for n from 2 to 100 do pmean := round(sum(ifactors(n)[2][i][1], i=1..nops(ifactors(n)[2]))/nops(ifactors(n)[2])): emean := round(sum(ifactors(n)[2][i][2], i=1..nops(ifactors(n)[2]))/nops(ifactors(n)[2])): printf(`%d, `, pmean^emean) od:

MATHEMATICA

a[n_] := Floor[1/2+(Plus@@First/@(fn=FactorInteger[n]))/(lth=Length[fn])]^Floor[1/2+(Plus@@Last/@fn)/lth]

CROSSREFS

Sequence in context: A081810 A071829 A229998 * A319677 A294650 A053585

Adjacent sequences:  A067617 A067618 A067619 * A067621 A067622 A067623

KEYWORD

easy,nonn

AUTHOR

Joseph L. Pe, Feb 02 2002

EXTENSIONS

Edited by Dean Hickerson and James A. Sellers, Feb 12 2002

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 December 13 08:08 EST 2018. Contains 318082 sequences. (Running on oeis4.)