A324039 Row lengths of the irregular triangles A324038 and A324246.

1, 1, 2, 2, 4, 8, 11, 19, 31, 50, 88, 146, 241, 407, 675, 1118, 1871, 3102, 5175, 8633, 14394, 23999, 40002, 66666, 111044, 185192, 308442, 514138, 857283, 1428537, 2381021

Offset

0,3

Links

Table of n, a(n) for n=0..30.

Formula

a(n) = 2*a(n-1) - a_1(n-1), for n >= 2, and a(0) = 1 = a(1), where a_1(k) is the number of entries 1 (mod 3) in row k of A324246 given in A324040(k).

Example

a(5) = 8 = 2*a(4) because a_1(4) =  A324040(4) = 0.
a(6) =  2*a(5) - 5 = 16 - 5 = 11  because a_1(5) = A324040(5) = 5.

Crossrefs

Cf. A324038, A324040, A324246.

Sequence in context: A050047 A056381 A245597 * A019463 A152763 A221666

Adjacent sequences: A324036 A324037 A324038 * A324040 A324041 A324042

Keyword

nonn,easy

Author

Nicolas Vaillant, Philippe Delarue, Wolfdieter Lang, May 09 2019

Status

approved