A=1+3+5+...+(2a+1)
=(a+1)(2a+1+1)/2
=(a+1)^2
B=1+3+5+...+(2b-1)
=b(2b-1+1)/2
=b^2
C=2+4+6+...+2c
=c(2c+2)/2
=c(c+1)
D=2+4+6+...+(2d+2)
=(d+1)(2d+2+2)/2
=(d+2)(d+1)
E=2+4+6+...+(2e-2)
=(e-1)(2e-2+2)/2
=e(e-1)