OFFSET
0,3
COMMENTS
Boustrophedon transform of A000169.
FORMULA
a(n) ~ (1 + sin(exp(-1)))/cos(exp(-1)) * n^(n-1). - Vaclav Kotesovec, Aug 17 2019
MATHEMATICA
nmax = 20; CoefficientList[Series[-(Sec[x] + Tan[x]) LambertW[-x], {x, 0, nmax}], x] Range[0, nmax]!
t[n_, 0] := If[n < 1, 0, n^(n - 1)]; t[n_, k_] := t[n, k] = t[n, k - 1] + t[n - 1, n - k]; a[n_] := t[n, n]; Array[a, 21, 0]
PROG
(Python)
from itertools import count, islice, accumulate
def A306881_gen(): # generator of terms
yield 0
blist = (0, )
for i in count(1):
yield (blist := tuple(accumulate(reversed(blist), initial=i**(i-1))))[-1]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Apr 16 2019
STATUS
approved