OFFSET
4,1
COMMENTS
An interval is linear of height k if it is isomorphic to the total order on k+1 elements.
See A394193 for the number of linear intervals of a given height.
PROG
(SageMath)
def a(n):
s = 1 + n/2
for k in range(2, n):
s += 2 * (n-k+1)/(k+1)
if k == 3:
s += 1/2
return s * factorial(n) * 2^(n-1)
print([a(n) for n in range(4, 20)])
CROSSREFS
KEYWORD
nonn
AUTHOR
Ludovic Schwob, Mar 12 2026
STATUS
approved