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Number A(n,k) of compositions of n such that no part equals any of its k immediate predecessors; square array A(n,k), n>=0, k>=0, read by antidiagonals.
6

%I #16 Oct 28 2018 11:04:41

%S 1,1,1,1,1,2,1,1,1,4,1,1,1,3,8,1,1,1,3,4,16,1,1,1,3,3,7,32,1,1,1,3,3,

%T 5,14,64,1,1,1,3,3,5,11,23,128,1,1,1,3,3,5,11,15,39,256,1,1,1,3,3,5,

%U 11,13,23,71,512,1,1,1,3,3,5,11,13,19,37,124,1024

%N Number A(n,k) of compositions of n such that no part equals any of its k immediate predecessors; square array A(n,k), n>=0, k>=0, read by antidiagonals.

%H Alois P. Heinz, <a href="/A261960/b261960.txt">Antidiagonals n = 0..50, flattened</a>

%e Square array A(n,k) begins:

%e : 1, 1, 1, 1, 1, 1, 1, ...

%e : 1, 1, 1, 1, 1, 1, 1, ...

%e : 2, 1, 1, 1, 1, 1, 1, ...

%e : 4, 3, 3, 3, 3, 3, 3, ...

%e : 8, 4, 3, 3, 3, 3, 3, ...

%e : 16, 7, 5, 5, 5, 5, 5, ...

%e : 32, 14, 11, 11, 11, 11, 11, ...

%p b:= proc(n, l) option remember;

%p `if`(n=0, 1, add(`if`(j in l, 0, b(n-j,

%p `if`(l=[], [], [subsop(1=NULL, l)[], j]))), j=1..n))

%p end:

%p A:= (n, k)-> b(n, [0$min(n, k)]):

%p seq(seq(A(n, d-n), n=0..d), d=0..12);

%t b[n_, l_] := b[n, l] = If[n==0, 1, Sum[If[MemberQ[l, j], 0, b[n-j, If[l == {}, {}, Append[Rest[l], j]]]], {j, 1, n}]]; A[n_, k_] := b[n, Array[0&, Min[n, k]]]; Table[A[n, d-n], {d, 0, 12}, {n, 0, d}] // Flatten (* _Jean-François Alcover_, Feb 08 2017, translated from Maple *)

%Y Columns k=0-2 give: A011782, A003242, A261962.

%Y Main diagonal gives A032020.

%Y Cf. A261959, A261981.

%K nonn,tabl

%O 0,6

%A _Alois P. Heinz_, Sep 06 2015