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A191907
Square array read by antidiagonals up: T(n,k) = -(n-1) if n divides k, else 1.
5
0, 1, 0, 1, -1, 0, 1, 1, 1, 0, 1, 1, -2, -1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, -3, 1, -1, 0, 1, 1, 1, 1, 1, -2, 1, 0, 1, 1, 1, 1, -4, 1, 1, -1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, -5, 1, -3, -2, -1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, -6, 1, 1, 1, 1, -1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, -4, 1, -2, 1, 0, 1, 1, 1, 1, 1, 1, 1, -7, 1, 1, 1, -3, 1, -1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0
OFFSET
1,13
COMMENTS
Apart from the top row, the same as A177121.
Sum_{k>=1} T(n,k)/k = log(n); this has been pointed out by Jaume Oliver Lafont in A061347 and A002162.
FORMULA
If n divides k then T(n,k) = -(n-1) else 1.
EXAMPLE
Table starts:
0..0..0..0..0..0..0..0..0...
1.-1..1.-1..1.-1..1.-1..1...
1..1.-2..1..1.-2..1..1.-2...
1..1..1.-3..1..1..1.-3..1...
1..1..1..1.-4..1..1..1..1...
1..1..1..1..1.-5..1..1..1...
1..1..1..1..1..1.-6..1..1...
1..1..1..1..1..1..1.-7..1...
1..1..1..1..1..1..1..1.-8...
MATHEMATICA
Clear[t, n, k];
nn = 30;
t[n_, k_] := t[n, k] = If[Mod[n, k] == 0, -(k - 1), 1]
MatrixForm[Transpose[Table[Table[t[n, k], {k, 1, nn}], {n, 1, nn}]]]
PROG
(PARI) N=20; M=matrix(N, N, n, k, if(n%k==0, 1-k, 1))~
CROSSREFS
KEYWORD
sign,tabl
AUTHOR
Mats Granvik, Jun 19 2011
STATUS
approved