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A270755
a(1) = 1; a(n) = min{(n-1-a(n-1));(n-1-i)}, where i (0<=i<=n-2) is the largest number such that a(n-1)=a(i) or i=0 if no such a(i) exists.
0
1, 0, 2, 1, 3, 2, 3, 2, 2, 1, 6, 5, 7, 6, 3, 8, 8, 1, 8, 2, 11, 10, 12, 11, 3, 10, 4, 23, 5, 17, 13, 18, 14, 19, 15, 20, 16, 21, 17, 9, 31, 10, 16, 6, 30, 15, 11, 23, 20, 13, 19, 17, 13, 3, 29, 26, 30, 12, 35, 24, 36, 25, 37, 26, 8, 46, 20, 18, 36, 8, 5, 42, 30, 16, 31, 34, 42, 5, 7, 66, 14, 48, 34, 49, 35, 26, 30, 14, 7, 10, 48, 9, 52, 41, 53, 42, 19, 63, 35, 14
OFFSET
1,3
COMMENTS
Sum_{i=1..n} a(n) ~ n*(n+1)/5.
EXAMPLE
a(1) = 1;
a(2) = min{(1-1);(1-0)} = 0;
a(3) = min{(2-0);(2-0)} = 2;
a(4) = min{(3-2);(3-0)} = 1;
a(5) = min{(4-1);(4-1)} = 3;
a(6) = min{(5-3);(5-0)} = 2;
a(7) = min{(6-2);(6-3)} = 3;
a(8) = min{(7-3);(7-5)} = 2;
a(9) = min{(8-2);(8-6)} = 2;
a(10) = min{(9-2);(9-8)} = 1;
and so on.
MATHEMATICA
a = {1}; Do[AppendTo[a, Min[n - 1 - a[[n - 1]], n - 1 - (If[MissingQ@#, 0, #] &@ SelectFirst[Range[n - 2, 1, -1], a[[n - 1]] == a[[#]] &])]], {n, 2, 120}]; a (* Michael De Vlieger, Mar 27 2016, Version 10.2 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Mar 22 2016
STATUS
approved