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Search: id:A092360
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| A092360 |
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Spiro-tribonacci numbers: a(n) = sum of three previous terms that are nearest when terms arranged in a spiral. |
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+0
2
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| 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; listen)
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OFFSET
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0,4
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EXAMPLE
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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
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CROSSREFS
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Cf. A078510, A092369.
Sequence in context: A147879 A147880 A020643 this_sequence A129141 A097431 A123929
Adjacent sequences: A092357 A092358 A092359 this_sequence A092361 A092362 A092363
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KEYWORD
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easy,nonn
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AUTHOR
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Michael Joseph Halm (hierogamous(AT)lycos.com), Apr 02 2004; corrected Apr 05 2004
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