2 6 10 14 18 4 8 12 16 20
x x x x x x x x x x
1 - -- - --- - ------- - ----------- - ---------------- + -- + ----- + --------- + -------------- + -------------------
2 720 3628800 87178291200 6402373705728000 24 40320 479001600 20922789888000 2432902008176640000
$$\frac{x^{20}}{2432902008176640000} - \frac{x^{18}}{6402373705728000} + \frac{x^{16}}{20922789888000} - \frac{x^{14}}{87178291200} + \frac{x^{12}}{479001600} - \frac{x^{10}}{3628800} + \frac{x^{8}}{40320} - \frac{x^{6}}{720} + \frac{x^{4}}{24} - \frac{x^{2}}{2} + 1$$
1 - x^2/2 - x^6/720 - x^10/3628800 - x^14/87178291200 - x^18/6402373705728000 + x^4/24 + x^8/40320 + x^12/479001600 + x^16/20922789888000 + x^20/2432902008176640000