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A127949
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A000012 as an infinite lower triangular matrix with all 1's; A127899 = a simple transform; then A000012 * A127899. Given A051340, change all 1's to -1. Triangle read by rows, (n-1) -1's followed by "n".
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3
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1, -1, 2, -1, -1, 3, -1, -1, -1, 4, -1, -1, -1, -1, 5, -1, -1, -1, -1, -1, 6, -1, -1, -1, -1, -1, -1, 7, -1, -1, -1, -1, -1, -1, -1, 8, -1, -1, -1, -1, -1, -1, -1, -1, 9, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 11, -1, -1, -1, -1, -1, -1
(list; table; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| For the inverse of A127949 see A126615, a harmonic triangle.
This is one way to define an inverse to A000217. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 30 2010]
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EXAMPLE
| First few rows of the triangle are:
1;
-1, 2;
-1, -1, 3;
-1, -1, -1, 4;
...
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MAPLE
| A127949 := proc(n) if issqr(1+8*n) then (sqrt(1+8*n)-1)/2 ; else -1 ; end if; end proc: seq(A127949(n), n=1..120) ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 30 2010]
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CROSSREFS
| Cf. A000012, A127899, A051340, A126615.
Sequence in context: A196931 A175465 A080209 * A167407 A051340 A165430
Adjacent sequences: A127946 A127947 A127948 * A127950 A127951 A127952
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KEYWORD
| tabl,sign,easy
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AUTHOR
| Gary W. Adamson (qntmpkt(AT)yahoo.com), Feb 09 2007
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 30 2010
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