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A299634
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Solution (a(n)) of the system of 3 complementary equations in Comments.
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35
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1, 4, 10, 12, 14, 17, 23, 26, 30, 37, 40, 42, 49, 50, 54, 58, 62, 64, 67, 68, 70, 76, 78, 86, 88, 90, 92, 95, 102, 104, 106, 110, 112, 118, 120, 126, 131, 138, 142, 144, 147, 150, 158, 160, 162, 164, 168, 170, 174, 182, 186, 192, 196, 198, 201, 210, 215, 218
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OFFSET
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0,2
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COMMENTS
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Define sequences a(n), b(n), c(n) recursively, starting with a(0) = 1, b(0) = 2:
a(n) = least new k >= 2*b(n-1);
b(n) = least new k;
c(n) = a(n) + b(n);
where "least new k" means the least positive integer not yet placed.
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The sequences a,b,c partition the positive integers.
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Let x = 11/6. Conjectures:
a(n) - 2*n*x = 0 for infinitely many n;
b(n) - n*x = 0 for infinitely many n;
c(n) - 3*n*x = 0 for infinitely many n;
(a(n) - 2*n*x) is unbounded below and above;
(b(n) - n*x) is unbounded below and above;
(c(n) - 3*n*x) is unbounded below and above;
***
Let d(a), d(b), d(c) denote the respective difference sequences. Conjectures:
12 occurs infinitely many times in d(a); 6 occurs infinitely many times in d(b);
2 occurs infinitely many times in d(c).
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LINKS
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EXAMPLE
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n: 0 1 2 3 4 5 6 7 8 9
a: 1 4 10 12 14 17 23 26 30 37
b: 2 5 6 7 8 11 13 15 18 20
c: 3 9 16 19 22 28 36 41 48 57
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MATHEMATICA
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z = 1000;
mex[list_, start_] := (NestWhile[# + 1 &, start, MemberQ[list, #] &]);
a = {1}; b = {2}; c = {}; AppendTo[c, Last[a] + Last[b]];
Do[{
AppendTo[a, mex[Flatten[{a, b, c}], 2 Last[b]]],
AppendTo[b, mex[Flatten[{a, b, c}], 1]],
AppendTo[c, Last[a] + Last[b]]}, {z}];
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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