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

Author

Pierre Abbat, Apr 12 2003

Keywords

• nonn
• tabf

Examples

			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,
...
		

Links

• Pierre Abbat, The 64-100 Sequences