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A047671
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Square array a(n,k) read by antidiagonals: a(n,1)=1, a(1,k)=1, a(n,k)=1+a(n-1,k-1)+a(n-1,k)+a(n,k-1).
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5
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1, 1, 1, 1, 4, 1, 1, 7, 7, 1, 1, 10, 19, 10, 1, 1, 13, 37, 37, 13, 1, 1, 16, 61, 94, 61, 16, 1, 1, 19, 91, 193, 193, 91, 19, 1, 1, 22, 127, 346, 481, 346, 127, 22, 1, 1, 25, 169, 565, 1021, 1021, 565, 169, 25, 1, 1, 28, 217, 862, 1933, 2524, 1933, 862
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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MAPLE
| A047671 := proc(n, k) option remember; if n = 1 then 1; elif k = 1 then 1; else 1+A047671(n-1, k-1)+A047671(n, k-1)+A047671(n-1, k); fi; end;
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CROSSREFS
| Main diagonal is A027618. Rows give A003215, A047672, A047673, A047674.
a(n, k)=A008288(n-1, k-1)+A047662(n-1, k-1).
Sequence in context: A157172 A131060 A124376 * A081577 A146986 A146771
Adjacent sequences: A047668 A047669 A047670 * A047672 A047673 A047674
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KEYWORD
| nonn,tabl,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Description corrected by Henry Bottomley (se16(AT)btinternet.com), May 09 2000.
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