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Triangle read by rows: Kreweras's "Rule A_4 left thickness" numbers.
1

%I #16 Apr 28 2019 12:01:19

%S 1,1,2,1,6,4,1,16,20,8,1,48,76,56,16,1,170,284,272,144,32,1,686,1128,

%T 1200,848,352,64,1,3008,4808,5280,4304,2432,832,128,1,13888,21688,

%U 23904,20848,13952,6592,1920,256,1,66354,101912,111856,100592,73952,42176,17152,4352,512

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

%H Lars Blomberg, <a href="/A259099/b259099.txt">Table of n, a(n) for n = 1..210 (the first 20 rows)</a>

%H G. Kreweras, <a href="http://www.numdam.org/item?id=BURO_1973__20__3_0">Sur les hiérarchies de segments</a>, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). See page 25.

%H G. Kreweras, <a href="/A001844/a001844.pdf">Sur les hiérarchies de segments</a>, Cahiers du Bureau Universitaire de Recherche Opérationnelle, Institut de Statistique, Université de Paris, #20 (1973). (Annotated scanned copy)

%F Kreweras gives a recurrence on page 24.

%e Triangle begins:

%e 1;

%e 1, 2;

%e 1, 6, 4;

%e 1, 16, 20, 8;

%e 1, 48, 76, 56, 16;

%e 1, 170, 284, 272, 144, 32;

%e 1, 686, 1128, 1200, 848, 352, 64;

%e 1, 3008, 4808, 5280, 4304, 2432, 832, 128;

%e 1, 13888, 21688, 23904, 20848, 13952, 6592, 1920, 256;

%e 1, 66354, 101912, 111856, 100592, 73952, 42176, 17152, 4352, 512;

%e ...

%K nonn,tabl

%O 1,3

%A _N. J. A. Sloane_, Jun 22 2015

%E More terms from _Lars Blomberg_, Apr 28 2019