Determine the 20th term of the sequence 1,4,

It is 58 
That's the 20th number in the sequence since each term is 3 more than the last number. An easy way to do this is multiply 19 times 3 because there are 19 terms after one. Then multiply by 3 because each term is 3 more than the last term. After you do 19 x 3 you get 57 right? Then add 57 to 1, the first term, to get 58.