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.

A094392 Antidiagonals of the tables formed from b(m,2,n,n), which is defined in Du 1989.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 5, 1, 1, 1, 1, 2, 8, 1, 1, 1, 1, 1, 3, 13, 1, 1, 1, 1, 1, 1, 5, 21, 1, 1, 1, 1, 1, 1, 2, 7, 34, 1, 1, 1, 1, 1, 1, 1, 3, 11, 55, 1, 1, 1, 1, 1, 1, 1, 1, 5, 16, 89, 1, 1, 1, 1, 1, 1, 1, 1, 2, 7, 25, 144, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 11, 37, 233, 1, 1, 1, 1, 1, 1, 1, 1, 1
Offset: 1

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Author

Amy Robinson (amylou(AT)mchsi.com), Apr 28 2004

Keywords

Examples

			E.g., for m = 5 and n = 2, b(5,2,2,2)= b(3,2,1,2) + b(4,2,2,2)= 2 because of the definition in the reference.
    1   1  1  1  1 1 1 1 1 1 1 1 1 1 1
    1   1  1  1  1 1 1 1 1 1 1 1 1 1 1
    2   1  1  1  1 1 1 1 1 1 1 1 1 1 1
    3   1  1  1  1 1 1 1 1 1 1 1 1 1 1
    5   2  1  1  1 1 1 1 1 1 1 1 1 1 1
    8   3  1  1  1 1 1 1 1 1 1 1 1 1 1
   13   5  2  1  1 1 1 1 1 1 1 1 1 1 1
   21   7  3  1  1 1 1 1 1 1 1 1 1 1 1
   34  11  5  2  1 1 1 1 1 1 1 1 1 1 1
   55  16  7  3  1 1 1 1 1 1 1 1 1 1 1
   89  25 11  5  2 1 1 1 1 1 1 1 1 1 1
  144  37 15  7  3 1 1 1 1 1 1 1 1 1 1
  233  57 23 11  5 2 1 1 1 1 1 1 1 1 1
  377  85 32 15  7 3 1 1 1 1 1 1 1 1 1
  610 130 49 23 11 5 2 1 1 1 1 1 1 1 1
		

Crossrefs

Cf. A006206 (A_{n,1}), A006207 (A_{n,2}), A006208 (A_{n,3}), A006209 (A_{n,4}), A130628 (A_{n,5}), A208092 (A_{n,6}), A006210 (D_{n,2}), A006211 (D_{n,3}), A094392.

Programs

  • Maple
    b := proc(k,i,j,n) option remember; if k = 1 then if i = 1 then return 0; end if; if i = 2 then if j = n then return 1; end if; return 0; end if; end if; if k = 2 then if i = 1 then return 1; end if; if i = 2 then if j = n then return 1; end if; return 0; end if; end if; if j = n then return b(k-2, i, 1, n) + b(k-1, i, n, n); end if; return b(k-2, i, 1, n) + b(k-2, i, j+1, n); end proc; # Chris Deugau (deugaucj(AT)uvic.ca), Dec 19 2005
  • Mathematica
    b[k_, i_, j_, n_] := b[k, i, j, n] = Which[k == 1, Which[i == 1, 0, i == 2 , If[j == n, 1, 0], True, 0], k == 2, Which[i == 1, 1, i == 2, If[j == n, 1, 0], True, 0], j == n, b[k - 2, i, 1, n] + b[k - 1, i, n, n], True, b[k - 2, i, 1, n] + b[k - 2, i, j + 1, n]];
    a[m_, n_] := b[m, 2, n, n];
    Table[a[m - n + 1, n], {m, 1, 14}, {n, m, 1, -1}] // Flatten (* Jean-François Alcover, Nov 21 2017, adapted from Maple *)

Formula

For i=2 and k >= 1 b(k+2, 2, n, n)=b(k, 2, 1, n) + b(k+1, 2, n, n). The remaining portion for the recurrence is defined in Du 1989.

Extensions

Corrected and extended by Chris Deugau (deugaucj(AT)uvic.ca), Dec 19 2005
Typo 891 -> 89,1 corrected by Jean-François Alcover, Nov 21 2017