Sequence #1:   -1, 2, 12, 40,...

Divide each by the corresponding terms
of the sequence of powers of 2 starting
with 20 which is 1.

Sequence #2:    1, 2,  4,  8,...

and we get this sequence

Sequence #3:   -1, 1,  3,  5,

which is the sequence of odd integers starting with -1.

The nth term of sequence #3 is 2n-3
The nth term of sequence #2 is 2n-1

So the nth term of sequence #1 is 

So you can get as many terms as you want.

-1, 2, 12, 40, 112, 288, 704, 1664, 3840, 8704, 19456, 43008,
94208, 204800, 442368, 950272, 2031616, 4325376, 9175040,
19398656, 40894464, 85983232, 180355072, 377487360, 788529152,
1644167168, 3422552064, 7113539584, 14763950080, 30601641984,
63350767616, 130996502528, 270582939648, 558345748480,
1151051235328, 2370821947392, 4879082848256, 10033043603456, 
20615843020800, 42331197669376, 86861418594304, 178120883699712,
365037860421632, 747667906887680, 1530520185864192,
3131409115906048, 6403555720167424, 13088586417045504, 26740122787512320,
54606145481867264, 111464090777419776, 227431781182210048,
463870761619161088, 945755921747804160, 1927540640514572288,
3927138875067072512, 7998392938210000896, 16285016252571713536,
33146493257446850560, 67445908019500548096, 137197659048214790144,
279007004114856968192, 567237380266568712192, 1152921504606846976000,
2342736497361113055232, 4759259971017064316928, 9666093894623805046784,
19627335694426962919424, 39844967199212631490560, 80870526019142674284544,
164102235279720171175936, 332926837042309987565568, 675298407050359265558528,
1369486280032197111971840, 2776751491927351385653248, 5629060847580617094725632,
11409237422613062836289536, 23120706300129782966255616, 46845875510066880519864320, 94900676839748390214434816,
192219205318726038778281984, 389274113915910594255388672, 788219634388738221908426752, 1595782081891310510612152320, 3230249790010289154814902272, 6537870832475914576810999808, 13230484169862501687984390144, 26770453349546348444693561344, 54159876718735387026836684800, 109557693476756154328572493824, 221591267032083069206943236096, 448134294221307659513482969088, 906172108756898361226158931968, 1832151258142362806850703851520, 3703916597541857782498179678208, 7487061357597979902589903306752,
15132579040224488480366894514176, 30582070730506034311107964829696, 61797966761126183322964281262080, 124863584122480596047425265729536,



Edwin