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A101474
Boustrophedon transform of the signed Jacobsthal numbers.
1
0, 1, 1, 3, 9, 21, 111, 393, 2309, 12321, 81071, 560033, 4301109, 35526921, 316858231, 3025055673, 30815437909, 333492212321, 3821573586591, 46224758487313, 588552491006709, 7868364598774521, 110201454736846151, 1613597716238974953, 24653957361927031509
OFFSET
0,4
COMMENTS
Boustrophedon transform of (-1)^n*A001045(n). Binomial transform is A101473.
FORMULA
E.g.f.: (sec(x)+tan(x))*(exp(x)-exp(-2*x))/3.
a(n) ~ n! * (exp(3*Pi/2)-1) * 2^(n+2) / (3 * exp(Pi) * Pi^(n+1)). - Vaclav Kotesovec, Jun 12 2015
PROG
(Python)
from itertools import accumulate, islice
def A101474_gen(): # generator of terms
blist, a, b = tuple(), 0, -1
while True:
yield (blist := tuple(accumulate(reversed(blist), initial=a)))[-1]
a, b = -b, -2*a-b
A101474_list = list(islice(A101474_gen(), 30)) # Chai Wah Wu, Jun 11 2022
CROSSREFS
Cf. A001045.
Sequence in context: A146248 A074000 A067645 * A298836 A252284 A259367
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Jan 21 2005
STATUS
approved