S1 = 1 + 2 + 3 + ... + 999
S1 = ( 999 + 1 ) × 999 : 2 =
S1 = 499500
...
S2 = 21 + 23 + 25 + ... + 1001
S2 = ( 1001 + 21 ) × 491 : 2
S2 = 250901
...
S3 = 15 + 17 + 19 + 21 + ... + 151 + 153 + 155
S3 = ( 155 + 15 ) × 71 : 2
S3 = 6035
...
S4 = 24 + 25 + 26 + ... + 125 + 126
S4 = ( 126 + 24 ) × 103 : 2
S4 = 7725
...
S5 = 10 + 12 + 14 + ... + 2010
S5 = ( 2010 + 10 ) × 1001 : 2
S5 = 1011010
...
S6 = 1 + 4 + 7 + ... + 79
S6 = ( 79 + 1 ) × 27 : 2
S6 = 1040
...
S7 = 15 + 25 + 35 + ... + 115
S7 = ( 115 + 15 ) × 11 : 2
S7 = 715
`#cactus`