Найдите сумму первых двадцати членов последовательности заданной форму b=2n+1

Веселая формула. Распишу подробно.
b1 = 2*1 + 1 = 2 + 1 = 3
b2 = 2*2 + 1 = 4 + 1 = 5
b3 = 2*3 + 1 = 6 + 1 = 7
b4 = 2*4 + 1 = 8 + 1 = 9
b5 = 2*5 + 1 = 10 + 1 = 11
b6 = 2*6 + 1 = 12 + 1 = 13
b7 = 2*7 + 1 = 14 + 1 = 15
b8 = 2*8 + 1 = 16 + 1 = 17
b9 = 2*9 + 1 = 18 + 1 = 19
b10 = 2*10 + 1 = 20 + 1 = 21
b11 = 2*11 + 1 = 22 + 1 = 23
b12 = 2*12 + 1 = 24 + 1 = 25
b13 = 2*13 + 1 = 26 + 1 = 27
b14 = 2*14 + 1 = 28 + 1 = 29
b15 = 2*15 + 1 = 30 + 1 = 31
b16 = 2*16 + 1 = 32 + 1 = 33
b17 = 2*17 + 1 = 34 + 1 = 35
b18 = 2*18 + 1 = 36 + 1 = 37
b19 = 2*19 + 1 = 38 + 1 = 39
b20 = 2*20 + 1 = 40 + 1 = 41