A191907 - OEIS

A191907

Square array read by antidiagonals up: T(n,k) = -(n-1) if n divides k, else 1.

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

(list; table; graph; refs; listen; history; text; internal format)

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.

LINKS

Table of n, a(n) for n=1..136.

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

Cf. A002162, A002391, A016627, A191904.

Sequence in context: A198068 A358194 A121361 * A052343 A073484 A203947

Adjacent sequences: A191904 A191905 A191906 * A191908 A191909 A191910

KEYWORD

sign,tabl

AUTHOR

Mats Granvik, Jun 19 2011

STATUS

approved