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A081327
Smallest 3-smooth number m such that n-m is also 3-smooth, a(n)=0 if no such 3-smooth number exists.
3
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, 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, 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
OFFSET
1,6
FORMULA
a(n) = 0 iff A081326(n) = 0.
If a(n) > 0: a(n)+A081328(n) = n.
EXAMPLE
a(32) = 8 = 2^3, as 32 = 8 + 3*2^3.
MATHEMATICA
smooth3Q[n_] := n/2^IntegerExponent[n, 2]/3^IntegerExponent[n, 3] == 1;
a[n_] := Module[{m}, For[m = 1, m<n, m++, If[smooth3Q[m] && smooth3Q[n-m], Return[m]]]; 0];
Table[a[n], {n, 1, 1000}] (* Jean-François Alcover, Oct 14 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Mar 19 2003
STATUS
approved