A259099 Triangle read by rows: Kreweras's "Rule A_4 left thickness" numbers.

1, 1, 2, 1, 6, 4, 1, 16, 20, 8, 1, 48, 76, 56, 16, 1, 170, 284, 272, 144, 32, 1, 686, 1128, 1200, 848, 352, 64, 1, 3008, 4808, 5280, 4304, 2432, 832, 128, 1, 13888, 21688, 23904, 20848, 13952, 6592, 1920, 256, 1, 66354, 101912, 111856, 100592, 73952, 42176, 17152, 4352, 512

Offset

1,3

Links

Lars Blomberg, Table of n, a(n) for n = 1..210 (the first 20 rows)

G. Kreweras, Sur les hiérarchies de segments, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). See page 25.

G. Kreweras, Sur les hiérarchies de segments, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). (Annotated scanned copy)

Formula

Kreweras gives a recurrence on page 24.

Example

Triangle begins:
  1;
  1,   2;
  1,   6,   4;
  1,  16,  20,   8;
  1,  48,  76,  56,  16;
  1, 170, 284, 272, 144,  32;
  1, 686, 1128, 1200, 848, 352, 64;
  1, 3008, 4808, 5280, 4304, 2432, 832, 128;
  1, 13888, 21688, 23904, 20848, 13952, 6592, 1920, 256;
  1, 66354, 101912, 111856, 100592, 73952, 42176, 17152, 4352, 512;
  ...

Crossrefs

Sequence in context: A269479 A118040 A073387 * A125693 A094527 A054335

Adjacent sequences: A259096 A259097 A259098 * A259100 A259101 A259102

Keyword

nonn,tabl

Author

N. J. A. Sloane, Jun 22 2015

Extensions

More terms from Lars Blomberg, Apr 28 2019

Status

approved