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2014-10-12T11:14:42+03:00

5 = 1+1·4

9 = 1+2·4

13 =1+3·4

..................

101=1+25·4 ⇒S=1·25 + 4(1+2+3+.......+25) =25+4·25·26/2 = 1325

2 3 2