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A378588
Triangle read by rows: T(n,k) is the number of maximal chains in the poset of all k-ary words of length <= n, ordered by B covers A iff A_i <= B_{i+k} for all i in A and some k >= 0.
2
1, 1, 2, 1, 5, 6, 1, 16, 22, 23, 1, 57, 94, 102, 103, 1, 226, 446, 507, 517, 518, 1, 961, 2308, 2764, 2855, 2867, 2868, 1, 4376, 12900, 16333, 17121, 17248, 17262, 17263, 1, 21041, 77092, 103666, 110487, 111739, 111908, 111924, 111925, 1, 106534, 489430, 701819, 761751, 773888, 775758, 775975, 775993, 775994, 1, 563961, 3282956, 5038344, 5578041, 5696293, 5716382, 5719046, 5719317, 5719337, 5719338
OFFSET
1,3
FORMULA
T(n,k) = T(n,n) for k > n.
EXAMPLE
Triangle begins:
k=1 2 3 4 5 6 7
n=1 1;
n=2 1, 2;
n=3 1, 5, 6;
n=4 1, 16, 22, 23;
n=5 1, 57, 94, 102, 103;
n=6 1, 226, 446, 507, 517, 518;
n=7 1, 961, 2308, 2764, 2855, 2867, 2868;
...
T(3,3) = 6:
() < (1) < (1,1) < (1,1,1),
() < (1) < (1,1) < (1,2),
() < (1) < (1,1) < (2,1),
() < (1) < (2) < (1,2),
() < (1) < (2) < (2,1),
() < (1) < (2) < (3).
PROG
(Python)
def mchains(n, k):
B, d1, S1 = [1, 1], {(1, ): 1}, {(1, )}
for i in range(n-1):
d2, S2 = dict(), set()
for j in S1:
for x in [j+(1, ), (1, )+j]+[j[:z]+tuple([j[z]+1])+j[z+1:] for z in range(len(j)) if j[z] < k]:
if x not in S2: S2.add(x); d2[x] = d1[j]
elif x != tuple([1]*(i+2)): d2[x] += d1[j]
B.append(sum(d2.values())); d1 = d2; S1 = S2
return B[:n+1]
def A378588_list(max_n):
B = [mchains(max_n, i+1) for i in range(max_n)]
return [[B[k][j+1] for k in range(j+1)] for j in range(max_n)]
CROSSREFS
Cf. A034841, A143672, A282698, A317145, column k=2 A378382, main diagonal A378608.
Sequence in context: A217204 A179455 A039810 * A328297 A124575 A178121
KEYWORD
nonn,tabl
AUTHOR
John Tyler Rascoe, Dec 01 2024
STATUS
approved