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

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);
v = Vec(serlaplace(sqrt(-1+sqrt(1+3*cos(2*x)^2))/cos(2*x)));
vector((#v+1)\2, k, v[2*k-1])

Crossrefs

Sequence in context: A062596 A142415 A068987 * A209077 A141139 A141130

Adjacent sequences: A273044 A273045 A273046 * A273048 A273049 A273050

Keyword

sign

Author

Gheorghe Coserea, May 13 2016

Status

approved