A377855 Cogrowth sequence of the 16-element group C4:C4 = .

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

Author

Sean A. Irvine, Nov 09 2024

Keywords

• nonn
• easy

Comments

Gives the even terms, all the odd terms are 0.

Links

• Index entries for linear recurrences with constant coefficients, signature (2, 4, 8, 32).

Crossrefs

Cf. A070775 (C4 X C4), A377840 (C8 X C2).

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)).