The Pell sequence is named after the English mathematician John Pell. It is formed recursively with the formula
or as a closed formula
The first numbers are
0,
1,
2,
5,
12,
29,
70,
169,
408,
985,
2378,
5741,
13860,
33461,
80782,
195025,
470832,
1136689,
2744210,
6625109,
15994428,
38613965,
93222358,
225058681,
543339720,
1311738121,
3166815962,
7645370045,
18457556052,
44560482149,
107578520350,
259717522849