A066201 Array read by antidiagonals upwards: for n-th row (n>=0), T(n,0) = 1; for k > 0, T(n,k) = T(n,k-1)-(n+k-1) if this is positive and has not already appeared in this row, otherwise T(n,k) = T(n,k-1)+(n+k-1).

1, 1, 1, 1, 2, 2, 1, 3, 4, 4, 1, 4, 6, 7, 7, 1, 5, 8, 2, 3, 3, 1, 6, 10, 3, 7, 8, 8, 1, 7, 12, 4, 9, 13, 14, 14, 1, 8, 14, 5, 11, 2, 20, 21, 21, 1, 9, 16, 6, 13, 3, 10, 12, 13, 13, 1, 10, 18, 7, 15, 4, 12, 19, 21, 22, 22, 1, 11, 20, 8, 17, 5, 14, 2, 29, 11, 12, 12

Offset

0,5

Links

Seiichi Manyama, Antidiagonals n = 0..139, flattened

Index entries for sequences related to Recamán's sequence

Example

Array begins
   1, 1,  2, 4,  7,  3,  8, 14, 21, 13, ...
   1, 2,  4, 7,  3,  8, 14, 21, 13, 22, ...
   1, 3,  6, 2,  7, 13, 20, 12, 21, 11, ...
   1, 4,  8, 3,  9,  2, 10, 19, 29, 18, ...
   1, 5, 10, 4, 11,  3, 12,  2, 13, 25, ...
   1, 6, 12, 5, 13,  4, 14,  3, 15,  2, ...
   1, 7, 14, 6, 15,  5, 16,  4, 17,  3, ...
   1, 8, 16, 7, 17,  6, 18,  5, 19,  4, ...

Mathematica

T[_, 0] = 1; T[n_, k_] := T[n, k] = If[t = T[n, k-1] - (n+k-1); t > 0 && FreeQ[Table[T[n, j], {j, 0, k-1}], t], t, T[n, k-1] + (n+k-1)]; Table[ T[n-k, k], {n, 0, 12}, {k, 0, n}] // Flatten (* Jean-François Alcover, Feb 18 2018 *)

Crossrefs

Rows give A063733, A063733, A005132, A066199, A066200.

Sequence in context: A089692 A365519 A349346 * A303273 A193820 A216368

Adjacent sequences: A066198 A066199 A066200 * A066202 A066203 A066204

Keyword

nonn,easy,tabl,look

Author

N. J. A. Sloane, Dec 16 2001

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 05 2003

Status

approved