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A092360 Spiro-tribonacci numbers: a(n) = sum of three previous terms that are nearest when terms arranged in a spiral. 1
0, 1, 1, 3, 5, 8, 13, 14, 28, 43, 45, 89, 135, 138, 143, 284, 430, 438, 451, 897, 1356, 1404, 1446, 2878, 4352, 4423, 4511, 4645, 9245, 13979, 14203, 14476, 14757, 15184, 30225, 45693, 46407, 47275, 48164, 49512, 98573, 148982, 151235, 153968, 156749 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

LINKS

Table of n, a(n) for n=0..44.

EXAMPLE

Terms are written in square boxes radiating spirally (cf. Ulam prime spiral). a(0) = 0, a(1) = 1 and a(2) = 1, so write 0, then 1 to its right. and another 1 below the first 1. The next unfilled box forms a square with the three filled boxes, so a(3) = a(0) + a(1) + a(2) = 0 + 1 + 1 = 2.

..............

... 8 13 14 28

... 5 .0 .1..

... 3 .2 .1..

.............

a(4) = 2 because a(0) + a(1) + a(2) = 0 + 1 + 1 = 2

CROSSREFS

Cf. A078510, A092369.

Sequence in context: A276527 A020643 A131354 * A129141 A289013 A097431

Adjacent sequences:  A092357 A092358 A092359 * A092361 A092362 A092363

KEYWORD

easy,nonn

AUTHOR

Michael Joseph Halm, Apr 02 2004; corrected Apr 05 2004

STATUS

approved

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Last modified August 18 15:59 EDT 2017. Contains 290727 sequences.