cp's OEIS Frontend

A205565 Number of ways of writing n = u + v with u <= v, and u,v having in ternary representation no 3.

%I A205565 #9 Jul 13 2013 12:04:21
%S A205565 1,1,1,1,2,1,1,1,1,1,2,1,2,4,2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,4,2,1,
%T A205565 2,1,2,4,2,4,8,4,2,4,2,1,2,1,2,4,2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,4,
%U A205565 2,1,2,1,1,1,1,1,2,1,1,1,1,1,2,1,2,4
%N A205565 Number of ways of writing n = u + v with u <= v, and u,v having in ternary representation no 3.
%H A205565 Reinhard Zumkeller, <a href="/A205565/b205565.txt">Table of n, a(n) for n = 0..10000</a>
%e A205565 a(30) = #{0+30, 3+27} = 2;
%e A205565 a(31) = #{0+31, 1+30, 3+28, 4+27} = 4;
%e A205565 a(32) = #{1+31, 4+28} = 2;
%e A205565 a(33) = #{3+30} = 1;
%e A205565 a(34) = #{3+31, 4+30} = 2;
%e A205565 a(35) = #{4+31} = 1;
%e A205565 a(36) = #{0+36, 9+27} = 2;
%e A205565 a(37) = #{0+37, 1+36, 9+28, 10+27} = 4;
%e A205565 a(38) = #{1+37, 10+28} = 2;
%e A205565 a(39) = #{0+39, 3+36, 9+30, 12+27} = 4;
%e A205565 a(40) = #{0+40, 1+39, 3+37, 4+36, 9+31, 10+30, 12+28, 13+27} = 8.
%o A205565 (Haskell)
%o A205565 a205565 n = sum $ map (a039966 . (n -)) $
%o A205565                   takeWhile (<= n `div` 2) a005836_list
%Y A205565 Cf. A039966, A005836, A120880.
%K A205565 nonn
%O A205565 0,5
%A A205565 _Reinhard Zumkeller_, Jan 28 2012