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A140756
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Count up to k sequence with alternating signs (k always positive).
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1
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1, -1, 2, 1, -2, 3, -1, 2, -3, 4, 1, -2, 3, -4, 5, -1, 2, -3, 4, -5, 6, 1, -2, 3, -4, 5, -6, 7, -1, 2, -3, 4, -5, 6, -7, 8, 1, -2, 3, -4, 5, -6, 7, -8, 9, -1, 2, -3, 4, -5, 6, -7, 8, -9, 10, 1, -2, 3, -4, 5, -6, 7, -8, 9, -10, 11, -1, 2, -3, 4, -5, 6, -7, 8, -9, 10, -11, 12, 1, -2, 3, -4, 5, -6, 7, -8, 9, -10, 11, -12, 13
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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Row sums are A004526(n+1).
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LINKS
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Table of n, a(n) for n=1..91.
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FORMULA
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Regarded as a triangle, T(n,k) = (-1)^{n-k} * k.
a(n)=A002260(n)*(-1)^(A004736(n)+1); a(n)=i*(-1)^(j+1), where i=n-t*(t+1)/2, j=(t*t+3*t+4)/2-n, t=floor((-1+sqrt(8*n-7))/2). - Boris Putievskiy, Mar 14 2013
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EXAMPLE
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Triangle begins:
1;
-1, 2;
1, -2, 3;
-1, 2, -3, 4;
1, -2, 3, -4, 5;
-1, 2, -3, 4, -5, 6;
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CROSSREFS
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Cf. A002260, A140757, A004736.
Sequence in context: A138060 A023121 A136261 * A002260 A243732 A194905
Adjacent sequences: A140753 A140754 A140755 * A140757 A140758 A140759
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KEYWORD
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easy,sign,tabl
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AUTHOR
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Franklin T. Adams-Watters, May 27 2008
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STATUS
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approved
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