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In an geometric progression s1=3 , b2=6
If s1 = 3 then b1 = 3
r = b2/b1 = 6/3 = 2
sn = b1(rn-1)/(r-1)
s2015 = b1(22015-1)/(2-1)
s2015 = 3(22015-1)/1
s2015 = 3(22015-1) = 11286583986824031675018443500857084975732991938612709298775419160092012655991557133336505414285783235806291210787102354048094558232868179130049475603660667473670634452940778373187709745388589371040949238831200951807011926538294561729477052927882004460755844781653596452514492868751194028396003087676571583906857180428808208934736312874557183646197492269098172683063128145643635487431355396105299678001614677507643449487558749047200550960482207326359475594910311244158234569957999120137592696722223652807184917356582602230498799100175848686444407270658797585246014223236088735742489275966637819607354183778301
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