login
Square array read by antidiagonals of T(n,k) = sign(n-k).
0

%I #14 Jun 24 2017 00:55:17

%S 0,-1,1,-1,0,1,-1,-1,1,1,-1,-1,0,1,1,-1,-1,-1,1,1,1,-1,-1,-1,0,1,1,1,

%T -1,-1,-1,-1,1,1,1,1,-1,-1,-1,-1,0,1,1,1,1,-1,-1,-1,-1,-1,1,1,1,1,1,

%U -1,-1,-1,-1,-1,0,1,1,1,1,1,-1,-1,-1,-1,-1,-1,1,1,1,1,1,1,-1,-1,-1,-1,-1,-1,0,1,1,1,1,1,1,-1,-1,-1,-1,-1,-1,-1,1,1,1,1

%N Square array read by antidiagonals of T(n,k) = sign(n-k).

%F a(n) = sign(A002260(n) - A004736(n)) or a(n) = sign((n-t(t+1)/2) - (t*t+3*t+4)/2-n)) where t = floor((-1+sqrt(8*n-7))/2). - _Boris Putievskiy_, Dec 24 2012

%e The start of the array is:

%e 0;

%e -1,...1;

%e -1,...0,...1;

%e -1,..-1,...1,...1;

%e -1,..-1,...0,...1,...1;

%e . . .

%e - _Boris Putievskiy_, Dec 24 2012

%Y Cf. A049581, A057427, A057428, A002260, A004736. As a straight sequence, a(n)=0 when n is in A046092. A023532 seen as a triangle is half this square.

%K easy,sign,tabl

%O 0,1

%A _Henry Bottomley_, Mar 06 2002