a1+a2+.+a2014
=1/2×4+1/4×6+1/6×8+……+1/4024×4026
=1/2 (1/2-1/4+1/4-1/6+1/6-1/8+……+1/4024-1/4026)
=1/2(1/2-1/4026)
=1/2×4024/2×4026
=1006/4026
=503/2013
a1+a2+.+a2014
=1/2×4+1/4×6+1/6×8+……+1/4024×4026
=1/2 (1/2-1/4+1/4-1/6+1/6-1/8+……+1/4024-1/4026)
=1/2(1/2-1/4026)
=1/2×4024/2×4026
=1006/4026
=503/2013