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.

A283941 Interspersion of the signature sequence of sqrt(5).

Original entry on oeis.org

1, 4, 2, 9, 6, 3, 16, 12, 8, 5, 25, 20, 15, 11, 7, 37, 30, 24, 19, 14, 10, 51, 43, 35, 29, 23, 18, 13, 67, 58, 49, 41, 34, 28, 22, 17, 85, 75, 65, 56, 47, 40, 33, 27, 21, 106, 94, 83, 73, 63, 54, 46, 39, 32, 26, 129, 116, 103, 92, 81, 71, 61, 53, 45, 38, 31
Offset: 1

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Author

Clark Kimberling, Mar 19 2017

Keywords

Comments

Row n is the ordered sequence of numbers k such that A023117(k)=n. As a sequence, A283941 is a permutation of the positive integers. This is a transposable interspersion; i.e., every row intersperses all other rows, and every column intersperses all other columns.

Examples

			Northwest corner:
  1   4   9   16  25  37  51  67
  2   6   12  20  30  43  58  76
  3   8   15  24  35  49  65  83
  5   11  19  29  41  56  73  92
  7   14  23  34  47  63  81  101
  10  18  28  40  54  71  90  111
		

Crossrefs

Programs

  • Mathematica
    r = Sqrt[5]; z = 100;
    s[0] = 1; s[n_] := s[n] = s[n - 1] + 1 + Floor[n*r];
    u = Table[n + 1 + Sum[Floor[(n - k)/r], {k, 0, n}], {n, 0, z}] (* A022780 , col 1 of A283941 *)
    v = Table[s[n], {n, 0, z}] (* A022779, row 1 of A283941*)
    w[i_, j_] := u[[i]] + v[[j]] + (i - 1)*(j - 1) - 1;
    Grid[Table[w[i, j], {i, 1, 10}, {j, 1, 10}]] (* A283941, array *)
    Flatten[Table[w[k, n - k + 1], {n, 1, 20}, {k, 1, n}]] (* A283941, sequence *)
  • PARI
    r = sqrt(5);
    z = 100;
    s(n) = if(n<1, 1, s(n - 1) + 1 + floor(n*r));
    p(n) = n + 1 + sum(k=0, n, floor((n - k)/r));
    u = v = vector(z + 1);
    for(n=1, 101, (v[n] = s(n - 1)));
    for(n=1, 101, (u[n] = p(n - 1)));
    w(i, j) = u[i] + v[j] + (i - 1) * (j - 1) - 1;
    tabl(nn) = {for(n=1, nn, for(k=1, n, print1(w(k, n - k + 1), ", "); );
    print(); ); };
    tabl(20) \\ Indranil Ghosh, Mar 21 2017
    
  • Python
    from sympy import sqrt
    import math
    def s(n): return 1 if n<1 else s(n - 1) + 1 + int(math.floor(n*sqrt(5)))
    def p(n): return n + 1 + sum([int(math.floor((n - k)/sqrt(5))) for k in range(0, n+1)])
    v=[s(n) for n in range(0, 101)]
    u=[p(n) for n in range(0, 101)]
    def w(i,j): return u[i - 1] + v[j - 1] + (i - 1) * (j - 1) - 1
    for n in range(1, 11):
        print([w(k, n - k + 1) for k in range(1, n + 1)]) # Indranil Ghosh, Mar 21 2017

Extensions

Edited by Clark Kimberling, Feb 27 2018