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A367736
a(0) = 1; for n > 0, a(n) is the coefficient of x^a(n-1) in the expansion of Product_{k=0..n-1} (x^a(k) + 1 + 1/x^a(k)).
0
1, 1, 2, 4, 6, 11, 19, 32, 58, 97, 163, 290, 501, 856, 1483, 2561, 4424, 7652, 13273, 23024, 39784, 69001, 119614, 207042, 358746, 621117, 1075865, 1864050, 3227724, 5590548, 9682402, 16770033, 29049713, 50310453, 87142439, 150939346, 261424583, 452810957
OFFSET
0,3
MATHEMATICA
a[0] = 1; a[n_] := a[n] = Coefficient[Product[x^a[k] + 1 + 1/x^a[k], {k, 0, n - 1}], x, a[n - 1]]; Table[a[n], {n, 0, 28}]
PROG
(Python)
from itertools import islice
from collections import Counter
def A367736_gen(): # generator of terms
c, b = {0:1}, 1
while True:
yield b
d = Counter(c)
for k in c:
e = c[k]
d[k+b] += e
d[k-b] += e
c = d
b = c[b]
A367736_list = list(islice(A367736_gen(), 20)) # Chai Wah Wu, Feb 05 2024
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Ilya Gutkovskiy, Jan 24 2024
EXTENSIONS
a(29)-a(37) from Chai Wah Wu, Feb 05 2024
STATUS
approved