A085004 a(n)=2*A085003(n)-n.

1, 2, 1, 0, -1, 0, 1, 0, -1, -2, -1, 0, 1, 0, -1, 0, 1, 2, 1, 0, 1, 2, 3, 2, 1, 0, 1, 2, 1, 0, -1, 0, 1, 2, 1, 0, 1, 2, 3, 2, 1, 2, 3, 4, 3, 2, 1, 2, 3, 2, 1, 0, 1, 2, 1, 0, -1, 0, 1, 2, 1, 0, 1, 2, 3, 2, 1, 0, 1, 2, 1, 0, -1, 0, 1, 0, -1, -2, -1, 0, 1, 0, -1, 0, 1, 2, 1, 0, -1, 0, 1, 0, -1, -2, -1, 0, -1, -2, -3, -2, -1, 0, -1, -2, -1, 0, 1, 0, -1, 0, 1, 2, 1, 0, -1

Offset: 1

Author

Benoit Cloitre, Jun 17 2003

Keywords

• sign

Crossrefs

Cf. A083035, A083036, A083037, A083038, A085003, A085005.

Programs

PARI

2*sum(k=1, n, (k+sqrtint(5*k^2))%4>1)-n \\ Charles R Greathouse IV, Feb 07 2013

Formula

|a(n+1)-a(n)| = 1. - Charles R Greathouse IV, Feb 07 2013