Solution:
⇒ 1 + 49 + 49^2 + .................... + 49^125 = (49^126 - 1) / ( 49 - 1)
⇒ ( 49^63 +1) (49^63 -1) /48
⇒ ( 49^63 +1 )( (1 + 48)^63 ) - 1) /48
⇒ (49^63 +1) ( 1+ 48 I - 1) ,Where is an integer
= (49^63 + 1) I
Greatest positive integer is k = 63