A081880 Triangle read by rows: n-th row gives trajectory of 2n under the map x->(x^2-4)/6, stopping when the next term would be negative or nonintegral.

0, 2, 0, 4, 2, 0, 6, 8, 10, 16, 42, 10, 16, 42, 12, 14, 32, 170, 4816, 3865642, 2490531345360, 16, 42, 18, 20, 66, 22, 80, 1066, 189392, 5978221610, 5956522269711832016, 5913359591595499145281505571167104042, 5827970276585748074286667660065476529979312208145367609757859954142122960, 24, 26

Offset

0,2

Links

Table of n, a(n) for n=0..35.

Pierre Abbat, The 64-100 Sequences

Example

8 -> (64-4)/6 = 10 -> (100-4)/6 = 16 -> (256-4)/6 = 42 -> (42^2-4)/6 nonintegral, so stop; thus row 4 is (8, 10, 16, 42).
Triangle begins:
0,
2, 0,
4, 2, 0,
6,
8,
10, 16, 42, 10, 16, 42,
12,
14, 32, 170, 4816, 3865642, 2490531345360,
16, 42,
18,
20, 66,
22, 80, 1066, 189392, 5978221610, 5956522269711832016, 5913359591595499145281505571167104042, 5827970276585748074286667660065476529979312208145367609757859954142122960,
24,
...

Crossrefs

Sequence in context: A366503 A185879 A356918 * A144289 A293815 A339941

Adjacent sequences: A081877 A081878 A081879 * A081881 A081882 A081883

Keyword

nonn,tabf

Author

Pierre Abbat, Apr 12, 2003

Status

approved