|
|
A134617
|
|
Numbers such that the arithmetic mean of the squares of their prime factors (taken with multiplicity) is a prime.
|
|
12
|
|
|
15, 20, 21, 28, 35, 39, 44, 48, 51, 52, 55, 65, 69, 85, 91, 92, 95, 108, 112, 115, 116, 129, 135, 141, 145, 159, 164, 172, 188, 189, 205, 208, 209, 215, 221, 225, 235, 236, 245, 249, 259, 268, 272, 295, 297, 299, 305, 309, 315, 316, 320, 325, 329, 339, 341, 365
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
EXAMPLE
|
a(2)=20, since 20=2*2*5 and (2^2+2^2+5^2)/3=33/3=11.
|
|
MATHEMATICA
|
amspQ[n_]:=PrimeQ[Mean[Flatten[Table[#[[1]], #[[2]]]&/@FactorInteger[ n]]^2]]; Select[Range[400], amspQ] (* Harvey P. Dale, Jan 21 2017 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
Minor edits by the author, May 06 2013
|
|
STATUS
|
approved
|
|
|
|