OFFSET
1,1
COMMENTS
Also numbers n such that the root mean square (quadratic mean) of the prime divisors of n is an integer.
These numbers are power of primes (p^k with k>=1) (A000961) or in A255580. - Daniel Lignon, Feb 26 2015
LINKS
Daniel Lignon, Table of n, a(n) for n = 1..1000
MAPLE
A005063 := proc(n) add(p^2, p=numtheory[factorset](n)) ; end: A001221 := proc(n) nops(numtheory[factorset](n)) ; end: isA144711 := proc(n) local sofpr ; sofpr := A001221(n) ; if sofpr <> 0 then issqr(A005063(n)/sofpr) ; else false ; fi; end: for n from 1 to 500 do if isA144711(n) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Sep 20 2008
MATHEMATICA
Select[Range[2, 1000], IntegerQ[RootMeanSquare[Select[Divisors[#], PrimeQ]]]&] (* Daniel Lignon, Feb 26 2015 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, Sep 19 2008
EXTENSIONS
More terms from R. J. Mathar, Sep 20 2008
STATUS
approved