The following program calculates Euler numbers.
Further informations are here.
10 ' Euler numbers
20 N=20:dim E(N):E(0)=1
30 for I=2 to N step 2:S=0
40 for J=0 to I-2 step 2
50 S=S+E(J)//!(J)//!(I-J)*(-1)^((I-J)\2)
60 next J
70 E(I)=S*(-1)*!(I)
80 print I,E(I)
90 next I