The numbers obtained by the s in the Lucas Sequence with and . They and the Pell-Lucas numbers
(the s in the Lucas Sequence) satisfy the recurrence relation

(1) |

(2) |

(3) |

(4) |

(5) |

(6) |

The only Triangular Pell number is 1 (McDaniel 1996).

**References**

McDaniel, W. L. ``Triangular Numbers in the Pell Sequence.'' *Fib. Quart.* **34**, 105-107, 1996.

Sloane, N. J. A. Sequences
A000129/M1413
and A002203/M0360
in ``An On-Line Version of the Encyclopedia of Integer Sequences.''
http://www.research.att.com/~njas/sequences/eisonline.html and Sloane, N. J. A. and Plouffe, S.
*The Encyclopedia of Integer Sequences.* San Diego: Academic Press, 1995.

© 1996-9

1999-05-26