OFFSET
0,2
COMMENTS
Boustrophedon transform of A000522.
MATHEMATICA
nmax = 21; CoefficientList[Series[(Sec[x] + Tan[x]) Exp[x]/(1 - x), {x, 0, nmax}], x] Range[0, nmax]!
t[n_, 0] := If[n < 1, 1, Floor[Exp[1] n!]]; t[n_, k_] := t[n, k] = t[n, k - 1] + t[n - 1, n - k]; a[n_] := t[n, n]; Array[a, 22, 0]
PROG
(Python)
from itertools import count, islice, accumulate
def A307593_gen(): # generator of terms
blist, m = tuple(), 1
for i in count(1):
yield (blist := tuple(accumulate(reversed(blist), initial=m)))[-1]
m = m*i + 1
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 17 2019
STATUS
approved