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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A283943 Interspersion of the signature sequence of e (a rectangular array, by antidiagonals).

Original entry on oeis.org

1, 4, 2, 10, 6, 3, 19, 13, 8, 5, 30, 23, 16, 11, 7, 44, 35, 27, 20, 14, 9, 61, 50, 40, 32, 24, 17, 12, 81, 68, 56, 46, 37, 28, 21, 15, 103, 89, 75, 63, 52, 42, 33, 25, 18, 128, 112, 97, 83, 70, 58, 48, 38, 29, 22, 156, 138, 121, 106, 91, 77, 65, 54, 43, 34
Offset: 1

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Author

Clark Kimberling, Mar 26 2017

Keywords

Comments

Row n is the ordered sequence of numbers k such that A023123(k) = n. As a sequence, A283943 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   10  19  30  44  61  81   103
  2  6   13  23  35  50  68  89   112
  3  8   16  27  40  56  75  97   121
  5  11  20  32  46  63  83  106  131
  7  14  24  37  52  70  91  115  141
  9  17  28  42  58  77  99  124  151
		

Crossrefs

Programs

  • Mathematica
    r = E; 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}] (* A022786, col 1 of A283943 *)
    v = Table[s[n], {n, 0, z}] (* A022785, row 1 of A283943 *)
    w[i_, j_] := u[[i]] + v[[j]] + (i - 1)*(j - 1) - 1;
    Grid[Table[w[i, j], {i, 1, 10}, {j, 1, 10}]] (* A283943, array *)
    Flatten[Table[w[k, n - k + 1], {n, 1, 20}, {k, 1, n}]] (* A283943, sequence *)
  • PARI
    \\ Produces the triangle when the array is read by antidiagonals
    r = exp(1);
    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(10) \\ Indranil Ghosh, Mar 26 2017
    
  • Python
    # Produces the triangle when the array is read by antidiagonals
    import math
    from mpmath import *
    mp.dps = 100
    def s(n): return 1 if n<1 else s(n - 1) + 1 + int(math.floor(n*e))
    def p(n): return n + 1 + sum([int(math.floor((n - k)/e)) 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 26 2017
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