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A278481
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Number of neighbors of the n-th term in a full isosceles triangle read by rows.
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3
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2, 4, 4, 4, 6, 4, 4, 6, 6, 4, 4, 6, 6, 6, 4, 4, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 4, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4
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OFFSET
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1,1
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COMMENTS
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Apart from the left border and the right border, the rest of the elements are 6's.
For the same idea but for a right triangle see A278480; for a square array see A278545, for a square spiral see A010731; and for a hexagonal spiral see A010722.
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LINKS
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EXAMPLE
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The sequence written as an isosceles triangle begins:
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. 2;
. 4, 4;
. 4, 6, 4;
. 4, 6, 6, 4;
. 4, 6, 6, 6, 4;
. 4, 6, 6, 6, 6, 4;
. 4, 6, 6, 6, 6, 6, 4;
. 4, 6, 6, 6, 6, 6, 6, 4;
. 4, 6, 6, 6, 6, 6, 6, 6, 4;
. 4, 6, 6, 6, 6, 6, 6, 6, 6, 4;
...
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CROSSREFS
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Left border gives A040002, the same as the right border.
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KEYWORD
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AUTHOR
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STATUS
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approved
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