A081327 - OEIS

%I #8 Oct 14 2021 12:57:15

%S 0,1,1,1,1,2,1,2,1,1,2,3,1,2,3,4,1,2,1,2,3,4,0,6,1,2,3,1,2,3,4,8,1,2,

%T 3,4,1,2,3,4,9,6,16,8,9,0,0,12,1,2,3,4,0,6,1,2,3,4,27,6,0,8,9,16,1,2,

%U 3,4,0,6,0,8,1,2,3,4,0,6,0,8,9,1,2,3,4,32,6,16,8,9,27,0,12,0,0,24,1,2,3,4,0

%N Smallest 3-smooth number m such that n-m is also 3-smooth, a(n)=0 if no such 3-smooth number exists.

%F a(n) = 0 iff A081326(n) = 0.

%F If a(n) > 0: a(n)+A081328(n) = n.

%e a(32) = 8 = 2^3, as 32 = 8 + 3*2^3.

%t smooth3Q[n_] := n/2^IntegerExponent[n, 2]/3^IntegerExponent[n, 3] == 1;

%t a[n_] := Module[{m}, For[m = 1, m<n, m++, If[smooth3Q[m] && smooth3Q[n-m], Return[m]]]; 0];

%t Table[a[n], {n, 1, 1000}] (* _Jean-François Alcover_, Oct 14 2021 *)

%Y Cf. A081329, A081330, A081328, A000040, A003586.

%K nonn

%O 1,6

%A _Reinhard Zumkeller_, Mar 19 2003