Can you please find what number comes next in the given series

Number which will come next in the series:
1, 3, 12, 36, ...
1, 3, 21, 123, ...

1).
Number which will come next in the series:
1, 3, 12, 36, ...
Ans: 144.
No number has digits more than 7.
All of them are 1, 3, 9, 27, 81, ...
converted to numbers in base 7

2).
Number which will come next in the series:
1, 3, 21, 123, ...
Ans: 1101..
No number has digits more than 4.
All of them are 1, 3, 9, 27, 81
converted to numbers in base 4.

tip 1: you can go to wolfram alpha

http://www.wolframalpha.com/

and type in

Expand[ InterpolatingPolynomial[ {1, 3, 12, 36}, n]]

to get a polynomial that generates those terms. you could do the same manually with some basic linear algebra.

tip 2: as you can see, we could do the same for

Expand[ InterpolatingPolynomial[ {1, 3, 12, 36, 0}, n]]

and

Expand[ InterpolatingPolynomial[ {1, 3, 12, 36, 100000}, n]]

the point being that these questions ("what number comes next in the sequence") are not phrased well (which is the fault of the textbook author, or teacher, or whatever).

A Gabillion

without more numbers i cant see the pattern yet