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A326328 a(n) = (2*n)! [x^(2*n)] cosh(x)^(-3). 1

%I #11 Nov 25 2021 12:42:34

%S 1,-3,33,-723,25953,-1376643,101031873,-9795436563,1212135593793,

%T -186388033956483,34859622790687713,-7791941518975112403,

%U 2051293521728340489633,-628173356956461494680323,221398076445213367209575553,-88980467736394156270609236243,40450409313733718675802456121473

%N a(n) = (2*n)! [x^(2*n)] cosh(x)^(-3).

%C Apparently all terms except the initial 1 have 3-valuation 1. - _F. Chapoton_, Nov 25 2021

%p egf := cosh(z)^(-3): ser := series(egf, z, 36):

%p seq((2*n)!*coeff(ser, z, 2*n), n=0..16);

%Y Row 3 of A326327.

%K sign

%O 0,2

%A _Peter Luschny_, Jul 07 2019

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)