A071374 0 iff n is of the form 4^a*(8k+7), otherwise 1.

1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1

Offset: 0

Author

N. J. A. Sloane, Jun 12 2002

Keywords

• nonn
• easy

Comments

0 iff n is not the sum of three squares.

Links

• Jean-Paul Allouche and Jeffrey Shallit, The ring of k-regular sequences, preprint.
• Jean-Paul Allouche and Jeffrey Shallit, The ring of k-regular sequences, Theoretical Computer Sci., Vol. 98 (1992), pp. 163-197.
• Index entries for 2-automatic sequences.

Crossrefs

1's complement to A072401. Cf. A071377.

Programs

PARI

a(n) = if(n, (n >> (2*valuation(n, 4))) % 8 < 7, 1); \\ Amiram Eldar, May 15 2025

Formula

From Amiram Eldar, May 15 2025: (Start)

a(n) = 1 - A072401(n);

Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 5/6. (End)