cp's OEIS Frontend

A317441 a(n) = number of k with 1 <= k <= n-1 such that a(k) and a(n-k) have the same binary length (A070939).

%I A317441 #12 Aug 02 2018 11:54:08
%S A317441 0,1,2,1,2,3,0,5,4,1,6,3,0,5,4,1,10,5,2,7,0,7,10,5,6,7,2,5,8,5,8,7,10,
%T A317441 9,6,7,8,7,10,11,6,7,8,11,6,17,8,9,8,19,8,13,10,15,6,19,10,9,6,19,8,
%U A317441 13,14,13,10,17,14,15,10,19,14,9,16,15,10,11,20
%N A317441 a(n) = number of k with 1 <= k <= n-1 such that a(k) and a(n-k) have the same binary length (A070939).
%C A317441 See A317420 for similar sequences.
%H A317441 Rémy Sigrist, <a href="/A317441/b317441.txt">Table of n, a(n) for n = 1..10000</a>
%H A317441 Rémy Sigrist, <a href="/A317441/a317441.png">Scatterplot of the first 500000 terms</a>
%e A317441 For n = 4:
%e A317441 - A070939(a(1)) = 1 <> 2 = A070939(a(3)),
%e A317441 - A070939(a(2)) = 1 =  1 = A070939(a(2)),
%e A317441 - A070939(a(3)) = 2 <> 1 = A070939(a(1)),
%e A317441 - hence a(4) = 1.
%o A317441 (PARI) l = vector(77); for (n=1, #l, l[n] = #binary(max(1, v=sum(k=1, n-1, l[k]==l[n-k]))); print1 (v ", "))
%Y A317441 Cf. A070939, A317420.
%K A317441 nonn,base
%O A317441 1,3
%A A317441 _Rémy Sigrist_, Jul 28 2018