|
| |
|
|
A101400
|
|
a(n) = a(n - 1) + 2*a(n - 2) + a(n - 3) - a(n - 4)
|
|
4
| |
|
|
1, 2, 5, 10, 21, 44, 91, 190, 395, 822, 1711, 3560, 7409, 15418, 32085, 66770, 138949, 289156, 601739, 1252230, 2605915, 5422958, 11285279, 23484880, 48872481, 101704562, 211649125, 440445850, 916576181, 1907412444, 3969361531
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
COMMENTS
| Lengths of successive words (starting with a) under the substitution: {a -> ab, b -> aac, c -> d, d -> b}.
|
|
|
EXAMPLE
| a(0) = 1, a(1) = 2, a(2) = 5, a(3) = 10, a(4) = 21, a(5) = 44
|
|
|
MATHEMATICA
| a[0] = 1; a[1] = 2; a[2] = 5; a[3] = 10; a[n_] := a[n] = a[n - 1] + 2a[n - 2] + a[n - 3] - a[n - 4]; Table[ a[n], {n, 0, 30}] (from Robert G. Wilson v Jan 15 2005)
|
|
|
CROSSREFS
| Cf. A092886, A105309.
Sequence in context: A101510 A066819 A114279 * A131403 A052540 A018106
Adjacent sequences: A101397 A101398 A101399 * A101401 A101402 A101403
|
|
|
KEYWORD
| nonn,easy
|
|
|
AUTHOR
| J. F. J. Laros (jlaros(AT)liacs.nl), Jan 15 2005
|
|
|
EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 15 2005
|
| |
|
|
