cp's OEIS Frontend

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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A257639 a(n) is the minimal position at which the maximal value of row n appears in row n of triangle A008289.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7
Offset: 1

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Author

Gheorghe Coserea, Nov 04 2015

Keywords

Comments

Except rows 3, 4, 10, 11, 21 of triangle A008289, all the other rows up to row number 10^6 contain a single maximal value.
Conjecture: for n >= 22 there is a unique maximal value in row n of triangle A008289.

Examples

			For n=9, a(9)=2 because A003056(9)=3 and max{Q(9,p), p=1..3}=4 and Q(9,2)=4.
		

Crossrefs

Programs

  • PARI
    Q(N) = {
      my(q = vector(N)); q[1] = [1, 0, 0, 0];
      for (n = 2, N,
        my(m = (sqrtint(8*n+1) - 1)\2);
        q[n] = vector((1 + (m>>2)) << 2); q[n][1] = 1;
        for (k = 2, m, q[n][k] = q[n-k][k] + q[n-k][k-1]));
      return(q);
    };
    seq(N) = {
      my(a = vector(N), q = Q(N), vmx = apply(vecmax, q));
      for (n = 1, N, a[n] = vecmin(select(v->v==vmx[n], q[n], 1)));
      a;
    };
    seq(86) \\ updated by Gheorghe Coserea, Jun 02 2018

Formula

a(n) = min argmax(k->Q(n,k), k=1..m), that is a(n) = min{k, Q(n,k) = max{Q(n,p), p=1..m}}, where m = A003056(n) and Q(n,k) is defined by A008289.
a(n) ~ K*sqrt(n) + O(1), where K = 2*sqrt(3)*log(2)/Pi = 0.76430413884... (A131266).
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