find

the first such no. is 1 and after that 5 and 9 and so on.

the last two digit no. will be 97.

so we have an A.P. with first term a=1 and last term l=97 and common difference d=4.

we have to find the sum of all terms of this A.P.

let us find out no. of terms in this A.P.

let no. of terms be n

then 97 = 1+(n-1)4 ==> n =25

sum of this A.P. = n/2(a+l) = 25/2(1+97) = 1225