OFFSET
1,1
COMMENTS
The numbers A100118(n)^2 are in the sequence.
FORMULA
sopfr(n) = 2*p, p prime.
EXAMPLE
36 is in the sequence because 36 = 2^2 * 3^2 => sum of prime factors = 2*2+3*2 = 10 = 2*5 where 5 is prime.
MAPLE
with(numtheory):A:= proc(n) local e, j; e := ifactors(n)[2]: add (e[j][1]*e[j][2], j=1..nops(e)) end: for m from 1 to 3000 do: if type(A(m)/2, prime)= true then printf(`%d, `, m):else fi:od:
MATHEMATICA
L = {}; Do[ww = Transpose[FactorInteger[k]]; w = ww[[1]].ww[[2]]; If[PrimeQ[w/2], AppendTo[L, k]], {k, 2, 500}]; L
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jun 02 2012
STATUS
approved