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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A336861 a(n) = ceiling((n-1-sqrt(n+1))/2).

Original entry on oeis.org

0, 0, 0, 1, 1, 2, 2, 2, 3, 3, 4, 4, 5, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 27, 28, 28, 29, 29, 30, 30, 31, 31, 32
Offset: 1

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Author

Edward Moody, Aug 16 2020

Keywords

Comments

a(n) is a lower bound for the number of items outside the instance of n-1 at one end of a Colombian variant Langford pairing (A336747). For example, one of the most lop-sided pairings for n=7 is 4 1 6 1 7 4 3 5 2 6 3 2 7 5, and there are a(n)=2 items to the left of the first '6'. This bound is tight until at least n=184.

Links

Crossrefs

Cf. A336747.

Programs

  • Magma
    [Ceiling((n-1-Sqrt(n+1))/2) : n in [1..100]]; // Wesley Ivan Hurt, Aug 21 2020
  • Mathematica
    Table[Ceiling[(n - 1 - Sqrt[n + 1])/2], {n, 1, 100}] (* Amiram Eldar, Aug 21 2020 *)
  • PARI
    a(n) = ceil((n-1-sqrt(n+1))/2); \\ Michel Marcus, Aug 19 2020
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