4+8+12+.+2000+2004+2008=几

问题描述:

4+8+12+.+2000+2004+2008=几

4+8+12+.+2000+2004+2008
=4*(1+2+3+...+500+501+502)
=4* (1+502)*502 /2
=4*503*502/2
=503*1004
=505012