A181652 -id:A181652 - cp's OEIS frontend

A181651 Eigentriangle of number triangle A070909.

1, 1, 1, 2, 1, 1, 3, 1, 1, 1, 6, 2, 2, 1, 1, 9, 3, 3, 1, 1, 1, 18, 6, 6, 2, 2, 1, 1, 27, 9, 9, 3, 3, 1, 1, 1, 54, 18, 18, 6, 6, 2, 2, 1, 1, 81, 27, 27, 9, 9, 3, 3, 1, 1, 1, 162, 54, 54, 18, 18, 6, 6, 2, 2, 1, 1

Offset: 0

Paul Barry, Nov 03 2010

First column is (essentially) A038754. Row sums are A068911. Inverse is A181652.
Generalized (conditional) Riordan array with k-th column generated by
  x^k*(1+x-x^2)/(1-3x^2) if k is even,
  (1+x-2x^2-x^3)/(1-3x^2) if k is odd.

			Triangle begins
    1;
    1,  1;
    2,  1,  1;
    3,  1,  1,  1;
    6,  2,  2,  1,  1;
    9,  3,  3,  1,  1,  1;
   18,  6,  6,  2,  2,  1,  1;
   27,  9,  9,  3,  3,  1,  1,  1;
   54, 18, 18,  6,  6,  2,  2,  1,  1;
   81, 27, 27,  9,  9,  3,  3,  1,  1,  1;
  162, 54, 54, 18, 18,  6,  6,  2,  2,  1,  1;

Paul Barry, Invariant number triangles, eigentriangles and Somos-4 sequences, arXiv preprint arXiv:1107.5490 [math.CO], 2011.

Cf. A038754, A068911, A070909, A181652.

cp's OEIS Frontend

A181651 Eigentriangle of number triangle A070909.

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