cp's OEIS Frontend

A317419 a(n) = number of k with 1 <= k <= n-1 such that a(k) AND a(n-k) = 0 (where AND denotes the bitwise AND operator).

%I A317419 #13 Aug 02 2018 11:53:56
%S A317419 0,1,2,2,4,4,4,6,8,8,6,6,8,8,8,10,12,12,10,14,20,14,8,10,12,12,8,8,12,
%T A317419 14,14,10,10,12,12,8,10,14,16,12,6,10,12,14,8,8,12,14,14,14,14,10,12,
%U A317419 12,8,12,18,16,12,8,10,14,18,14,10,18,18,16,12,14,18
%N A317419 a(n) = number of k with 1 <= k <= n-1 such that a(k) AND a(n-k) = 0 (where AND denotes the bitwise AND operator).
%C A317419 All terms are even except a(2) = 1.
%C A317419 See A317420 for similar sequences.
%H A317419 Rémy Sigrist, <a href="/A317419/b317419.txt">Table of n, a(n) for n = 1..10000</a>
%e A317419 For n = 4:
%e A317419 - a(1) AND a(3) = 0 AND 2 = 0,
%e A317419 - a(2) AND a(2) = 1 AND 1 = 1 <> 0,
%e A317419 - a(3) AND a(1) = 2 AND 0 = 0,
%e A317419 - hence a(4) = 2.
%o A317419 (PARI) a = vector(71); for (n=1, #a, a[n] = sum(k=1, n-1, bitand(a[k], a[n-k])==0); print1 (a[n] ", "))
%Y A317419 Cf. A317420.
%K A317419 nonn,base
%O A317419 1,3
%A A317419 _Rémy Sigrist_, Jul 27 2018