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 A127949 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". 3
 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; text; internal format)
 OFFSET 1,3 COMMENTS For the inverse of A127949 see A126615, a harmonic triangle. This is one way to define an inverse to A000217. - R. J. Mathar, Apr 30 2010 LINKS EXAMPLE First few rows of the triangle are: 1; -1, 2; -1, -1, 3; -1, -1, -1, 4; ... 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) ; # R. J. Mathar, Apr 30 2010 CROSSREFS Cf. A000012, A127899, A051340, A126615. Sequence in context: A196931 A175465 A080209 * A167407 A051340 A216764 Adjacent sequences:  A127946 A127947 A127948 * A127950 A127951 A127952 KEYWORD tabl,sign,easy AUTHOR Gary W. Adamson, Feb 09 2007 EXTENSIONS More terms from R. J. Mathar, Apr 30 2010 STATUS approved

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Last modified March 23 02:57 EDT 2019. Contains 321422 sequences. (Running on oeis4.)