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a(n) is the number of n-digit numbers in A376637.
2

%I #10 Oct 03 2024 11:02:30

%S 2,4,4,6,8,4,12,8,8,12,20,0,16,16,12,24,16,8,12,16,32,12,20,32,24,16,

%T 16,12,16,20,40,40,8,28,44,20,44,28,20,24,20,20,16,32,20,44,44,56,28,

%U 28,20,60,52,24,56,56,20,36,36,32,24,24,32,24,16,60,16,32

%N a(n) is the number of n-digit numbers in A376637.

%C All terms are even: if a word w belongs to A376637, then replacing 1's by 2's and 2's by 1's in w yields another word in A376637.

%C a(n)/2 is the number of terms of A376637 with digital sum n.

%H Rémy Sigrist, <a href="/A376638/b376638.txt">Table of n, a(n) for n = 1..8192</a>

%H Rémy Sigrist, <a href="/A376638/a376638.txt">C++ program</a>

%H <a href="/index/K#Kolakoski">Index entries for sequences related to Kolakoski sequence</a>

%e Sequence A376637 begins: 1, 2, 11, 12, 21, 22, 112, 122, 211, 221, 1121.

%e So a(1) = 2, a(2) = 4, a(3) = 4.

%o (C++) // See Links section.

%Y Cf. A007782, A376637.

%K nonn

%O 1,1

%A _Rémy Sigrist_, Sep 30 2024