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 A317585 a(n) = number of k with 1 <= k <= n-1 such that abs(a(k) - a(n-k)) <= 2. 2

%I #12 Aug 02 2018 11:54:24

%S 0,1,2,3,2,5,4,3,2,9,6,7,6,5,2,5,6,9,4,9,2,13,12,13,8,7,6,11,6,13,2,9,

%T 8,7,8,13,4,13,6,15,6,11,12,13,16,23,8,13,0,17,14,25,14,13,8,7,6,19,8,

%U 19,6,13,4,19,12,25,20,23,10,19,10,21,16,23,10

%N a(n) = number of k with 1 <= k <= n-1 such that abs(a(k) - a(n-k)) <= 2.

%C See A317420 for similar sequences.

%H Rémy Sigrist, <a href="/A317585/b317585.txt">Table of n, a(n) for n = 1..10000</a>

%H Rémy Sigrist, <a href="/A317585/a317585.png">Colored scatterplot of the first 100000 terms</a> (where the color is function of the parity of n)

%F For n = 5:

%F - |a(1) - a(4)| = |0 - 3| = 3 > 2,

%F - |a(2) - a(3)| = |1 - 2| = 1 <= 2,

%F - |a(3) - a(2)| = |2 - 1| = 1 <= 2,

%F - |a(4) - a(1)| = |3 - 0| = 3 > 2,

%F - hence a(5) = 2.

%o (PARI) a = vector(75); for (n=1, #a, a[n] = sum(k=1, n-1, abs(a[k]-a[n-k])<=2); print1 (a[n] ", "))

%Y Cf. A317420.

%K nonn

%O 1,3

%A _Rémy Sigrist_, Aug 01 2018

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Last modified August 15 02:04 EDT 2024. Contains 375171 sequences. (Running on oeis4.)