S = 3 2 n = 0 ∑ ∞ ( 2 ( 1 + 5 ) ) n ( 2 n + 1 ) n ! n ! ( − 1 ) n ( 2 n ) !
Given that S = B A ( C + D E ) ln ( G F ( H + I J ) ) , where
Input the least possible value of A + B + C + D + E + F + G + H + I + J as your answer.
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Let's generalise the series
It is known from Generating function and Taylor series that
n = 0 ∑ ∞ 2 2 n ( n ! ) 2 ( − 1 ) n ( 2 n ) ! x 2 n = 1 + x 2 1
Taking integral both sides from 0 to a
n = 0 ∑ ∞ ( 2 ) 2 n ( 2 n + 1 ) . ( n ! ) 2 ( − 1 ) n ( 2 n ) ! a 2 n + 1 = ∫ 0 a 1 + x 2 1 d x ⟹ n = 0 ∑ ∞ 2 2 n ( 2 n + 1 ) . ( n ! ) 2 ( − 1 ) n ( 2 n ) ! a 2 n + 1 = [ lo g ( x + x 2 + 1 ) ] 0 a = lo g ( a + a 2 + 1 ) Now put a = 1 + 5 2 = ϕ 1 The series becomes
1 + 5 2 n = 0 ∑ ∞ ( 2 ( 1 + 5 ) ) n ( 2 n + 1 ) ( n ! ) 2 ( − 1 ) n ( 2 n ) ! = lo g ( ϕ 1 + ϕ ) = 2 3 lo g ( 2 1 + 5 )
So 3 2 n = 0 ∑ ∞ ( 2 n + 1 ) ( 2 ( 1 + 5 ) ) n ( n ! ) 2 ( − 1 ) n ( 2 n ) ! = 2 1 + 5 lo g ( 2 1 + 5 ) Answer is A + B + C + D + E + F + G + H + I = 2 0