A273047 - OEIS

A273047

E.g.f.: sqrt(-1+sqrt(1+3*cos(2*x)^2))/cos(2*x) [even terms only].

1, 1, 2, -149, -14743, -1291124, -75141463, 16904078101, 12079897715342, 5127055781374651, 1591577436442791797, 16734787827095948776, -636181884940159502862223, -835452999214833112556297399, -749352506033895636346796223718, -390445159197257248842601279581749

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OFFSET

0,3

COMMENTS

The odd power terms are zero because the e.g.f. is even.

LINKS

Gheorghe Coserea, Table of n, a(n) for n = 0..200

EXAMPLE

1 + 1*x^2/2! + 2*x^4/4! - 149*x^6/6! - ...

PROG

(PARI)

x = 'x + O('x^31);