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A239093 Irregular triangle of incomplete tribonacci numbers t_n(s) (n >= 1, 0 <= s <= floor((n-1)/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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 8 14:36 EDT 2020. Contains 336298 sequences. (Running on oeis4.)