|
%I #13 Sep 19 2021 17:03:22
%S 256,588,693,3840,6561,14157,17787,141960,178360,313600,337365,350000,
%T 387072,390625,407442,432000,466560,531674,535815,541310,664909,
%U 697851,1044582,1262056,1264640,1299272,1374327,1547570,1608575,1660360
%N Composite numbers such that the cube root of the sum of cubes of their prime factors is an integer.
%H Hieronymus Fischer, <a href="/A134608/b134608.txt">Table of n, a(n) for n = 1..300</a>
%e a(3)=693, since 693=3*3*7*11 and (2*3^3+7^3+11^3)^(1/3)=1728^(1/3)=12.
%t criQ[n_]:=IntegerQ[Surd[Total[Flatten[Table[#[[1]],#[[2]]]&/@ FactorInteger[ n]]^3],3]]; Select[Range[1670000],CompositeQ[#] && criQ[#]&] (* _Harvey P. Dale_, Sep 19 2021 *)
%o (PARI) lista(m) = {for (i=2, m, if (! isprime(i), f = factor(i); s = sum (j=1, length(f~), f[j,1]^3*f[j,2]); if (ispower(s, 3), print1(i, ", "));););} \\ _Michel Marcus_, Apr 14 2013
%Y Cf. A001597, A025475, A134333, A134344, A134376.
%Y Cf. A134600, A134602, A134605, A134611, A134616, A134618, A134620.
%K nonn
%O 1,1
%A _Hieronymus Fischer_, Nov 11 2007
%E Minor edits by _Hieronymus Fischer_, Apr 20 2013
|
