A277728 Numbers not in any of A158919, A277722, A277723.

2, 4, 8, 15, 17, 19, 21, 26, 28, 32, 35, 39, 41, 46, 48, 52, 59, 61, 63, 65, 70, 72, 76, 78, 83, 85, 89, 92, 96, 100, 102, 107, 109, 113, 116, 120, 122, 127, 129, 133, 140, 144, 146, 151, 153, 157, 159, 164, 166, 170, 173, 177, 181, 184, 188, 190, 195, 197, 201, 203, 208, 210, 212, 214, 221

Offset: 1

Author

N. J. A. Sloane, Oct 30 2016

Keywords

• nonn

Comments

Let tau be the tribonacci constant (A058265). Although 1/tau + 1/tau^2 + 1/tau^3 = 1, by Uspensky's 1927 theorem, the three sequences floor(n*tau) (A158919), floor(n*tau^2) (A277722), and floor(n*tau^3) (A277723) cannot form a partition of the nonnegative integers. (Compare Beatty's theorem.)

Entries A277724-A277727 investigate how these three sequences meet, and the present sequence gives the numbers not in any of the three sequences. Any two of the three sequences have a nontrivial intersection, while the intersection of all three is {0}.

On the other hand, the three sequences A003144, A003145, A003146, which arise from the tribonacci word, DO form a partition of the positive integers and are closely connected with the three sequences mentioned in the definition.

It would be nice to have b-files for all the sequences mentioned here. (Many do, but some do not.)

Links

• Jean-François Alcover, Table of n, a(n) for n = 1..2955
• S. Beatty, A. Ostrowski, J. Hyslop, and A. C. Aitken, Problems and Solutions: Solutions: 3177, Amer. Math. Monthly, 34 (1927), pp. 159-160.
• R. L. Graham, On a theorem of Uspensky, Amer. Math. Mnthly, 70 (1963): 407-409.
• A. J. Hildebrand, Junxian Li, Xiaomin Li, Yun Xie, Almost Beatty Partitions, arXiv:1809.08690 [math.NT], 2018.
• J. V. Uspensky, On a problem arising out of the theory of a certain game, Amer. Math. Mnthly., 34 (1927), 516-521.

Crossrefs

Cf. A003144, A003145, A003146, A058265, A158919, A184820, A277722, A277723, A277724, A277725, A277726, A277727.

Programs

Mathematica

maxTerm = 10000;
a19[n_] := Floor[n*Root[#^3 - #^2 - # - 1&, 1]];
a22[n_] := Floor[n*Root[#^3 - 3 #^2 - # - 1&, 1]];
a23[n_] := Floor[n*Root[#^3 - 7 #^2 + 5 # - 1&, 1]];
A19 = Reap[k = 1; While[a19[k] <= maxTerm, Sow[a19[k++]]]][[2, 1]];
A22 = Reap[k = 1; While[a22[k] <= maxTerm, Sow[a22[k++]]]][[2, 1]];
A23 = Reap[k = 1; While[a23[k] <= maxTerm, Sow[a23[k++]]]][[2, 1]];
Select[Range[maxTerm], FreeQ[A19, #] && FreeQ[A22, #] && FreeQ[A23, #]&] (* Jean-François Alcover, Dec 06 2018 *)