Which sequence has 3n as its nth term

3n,   let n = 0, 1, 2, 3, 4, 5,

When n= 0,  3n = 3*0 = 0

When n= 1,  3n = 3*1= 3

When n= 2,  3n = 3*2 = 6

When n= 3,  3n = 3*3 = 9

When n= 4,  3n = 3*4 = 12

When n= 5,  3n = 3*5 = 15
...
Sequence   3n    =  0, 3, 6, 9, 12, 15,            for n = 0, 1, 2, 3, 4, 5,

It’s 13.8 because C^2-A^2=B^2
19^2-13^2=B^2
361-169=B^2
B^2=192
B= approx. 13.8