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A377840
Cogrowth sequence of the 16-element group C8 X C2 = <S,T | S^8, T^2, [S,T]>.
8
1, 1, 1, 1, 2, 46, 496, 3004, 12872, 43912, 130816, 394384, 1470944, 6874336, 33550336, 151869376, 622116992, 2353246336, 8589869056, 31961192704, 125858012672, 521796316672, 2199022206976, 9122012806144, 36758056208384, 144536687773696, 562949936644096
OFFSET
0,5
COMMENTS
Gives the even terms, all the odd terms are 0.
FORMULA
G.f.: (8*x^7+28*x^6+42*x^5-34*x^4+35*x^3-21*x^2+7*x-1) / ((4*x-1) * (4*x^2+1) * (4*x^4+8*x^3+8*x^2-4*x+1)).
EXAMPLE
a(4)=2 corresponds to the words SSSSSSSS and TTTTTTTT.
CROSSREFS
Cf. A007582 (D8), A377627 (C6 X C2), A377714 (C4 X C2).
Sequence in context: A281327 A302377 A303098 * A302949 A174592 A066555
KEYWORD
nonn,easy
AUTHOR
Sean A. Irvine, Nov 09 2024
STATUS
approved