

A239093


Irregular triangle of incomplete tribonacci numbers t_n(s) (n >= 1, 0 <= s <= floor((n1)/2)), read by rows.


0



1, 1, 1, 2, 1, 4, 1, 6, 7, 1, 8, 13, 1, 10, 23, 24, 1, 12, 37, 44, 1, 14, 55, 80, 81, 1, 16, 77, 140, 149, 1, 18, 103, 232, 273, 274, 1, 20, 133, 364, 493, 504, 1, 22, 167, 544, 865, 926, 927, 1, 24, 205, 780, 1461, 1692, 1705, 1, 26, 247, 1080, 2369, 3050, 3135, 3136, 1, 28, 293, 1452, 3693, 5376, 5753, 5768
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OFFSET

1,4


LINKS

Table of n, a(n) for n=1..72.
J. L. Ramirez and V. F. Sirvent, Incomplete Tribonacci Numbers and Polynomials, Journal of Integer Sequences, Vol. 17, 2014, #14.4.2.


FORMULA

t_{n+3}(s+1) = t_{n+2}(s+1) + t_{n+1}(s) + t_n(s).
The third column is (essentially) 2m^2+5.


EXAMPLE

Triangle begins:
1,
1,
1,2,
1,4,
1,6,7,
1,8,13,
1,10,23,24,
1,12,37,44,
1,14,55,80,81,
1,16,77,140,149,
1,18,103,232,273,274,
1,20,133,364,493,504,
...


CROSSREFS

Sequence in context: A128099 A182242 A261605 * A263453 A108952 A088522
Adjacent sequences: A239090 A239091 A239092 * A239094 A239095 A239096


KEYWORD

nonn,tabf


AUTHOR

N. J. A. Sloane, Mar 23 2014


STATUS

approved



