OFFSET
1,1
COMMENTS
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..45 (terms < 2*10^11)
EXAMPLE
512 = 2^9 is a term because 2^9 = 7^3 + 13^2.
MATHEMATICA
Select[Union@ Map[Total, Subsets[With[{nn = 10^6}, Complement[ Select[ Range@ nn, PrimePowerQ], Prime[Range[PrimePi@ nn]]]], {2}]], # == 1 ||
GCD @@ FactorInteger[#][[All, 2]] > 1 &] (* Michael De Vlieger, Feb 18 2017, after Harvey P. Dale at A246547 *)
PROG
(PARI) is(n) = if(!ispower(n), return(0), my(x=n-1, y=1); while(y < x, if(isprimepower(x) && isprimepower(y) && !ispseudoprime(x) && !ispseudoprime(y), return(1)); y++; x--)); 0 \\ Felix Fröhlich, Feb 18 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Altug Alkan, Feb 18 2017
EXTENSIONS
More terms from Felix Fröhlich, Feb 18 2017
a(28)-a(35) from Giovanni Resta, May 07 2017
STATUS
approved