If `S=1/(1+1^2+1^4)+2/(1+2^2+2^4)+3/(1+3^2+3^4)+.........oo,` then find the value of `14S.`

If S=(1)/(1.2)+(1.3)/(1.2.3.4)+(1.3.5)/(1.2.3.4.5.6)+...."to "oo , then S =

S_(n)=(1.2)/(3)+(2.3)/(3^(2))+(3.4)/(3^(3))......oo, then 4S is

1 + (1+2)/(2!) + (1+2+3)/(3!) + (1+2+3+4)/(4!) + ......oo

If (1)/(1^(2))+(1)/(2^(2))+(1)/(3^(2))+...oo=(pi^(2))/(6) then value of 1-(1)/(2^(2))+(1)/(3^(2))-(1)/(4^(2))+...oo=

If {:(1,2,4),(1,3,5),(1,4,a):} is singular then the value of a is