445 , 221 , 109 , 53 , . . .
"explanation : to obtain next number , subtract 3 from the previous number and divide the result by 2 445 ( 445 - 3 ) / 2 = 221 ( 221 - 3 ) / 2 = 109 ( 109 - 3 ) / 2 = 53 ( 53 - 3 ) / 2 = 25 answer : d"
subtract(negate(53), multiply(subtract(221, 109), divide(subtract(221, 109), subtract(445, 221))))