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A377855
Cogrowth sequence of the 16-element group C4:C4 = <S,T | S^4, T^4, STST^3>.
3
1, 0, 2, 6, 40, 120, 512, 2016, 8320, 32640, 131072, 523776, 2099200, 8386560, 33554432, 134209536, 536903680, 2147450880, 8589934592, 34359607296, 137439477760, 549755289600, 2199023255552, 8796090925056, 35184380477440, 140737479966720, 562949953421312
OFFSET
0,3
COMMENTS
Gives the even terms, all the odd terms are 0.
FORMULA
G.f.: (12*x^4+6*x^3+2*x^2+2*x-1) / ((4*x-1) * (2*x+1) * (4*x^2+1)).
CROSSREFS
Cf. A070775 (C4 X C4), A377840 (C8 X C2).
Sequence in context: A288491 A212883 A378272 * A336959 A027161 A081096
KEYWORD
nonn,easy
AUTHOR
Sean A. Irvine, Nov 09 2024
STATUS
approved