A169695 a(n) = 1 if n is a square, otherwise a(n) = 2.

1, 1, 2, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2

Offset: 0

Author

N. J. A. Sloane, Apr 15 2010

Keywords

• nonn
• easy

Comments

Also number of central divisors of n, if n >= 1. - Omar E. Pol, Feb 10 2011.

Length of n-th row in the array of A207375, if n >= 1. - Omar E. Pol, Feb 27 2012

Links

• Antti Karttunen, Table of n, a(n) for n = 0..65537
• Index entries for sequences computed from exponents in factorization of n.

Crossrefs

Cf. A010052, A275437.

Cf. A000005, A049240, A161840.

Programs

Mathematica

Array[2 - Boole[IntegerQ@ Sqrt@ #] &, 105, 0] (* Michael De Vlieger, Nov 03 2017 *)

PARI

a(n) = 2 - issquare(n); \\ Amiram Eldar, Apr 17 2024

Formula

From Omar E. Pol, Feb 10 2011: (Start)

a(n) = 2 - A010052(n).

a(n) = 1 + A049240(n), n >=1.

a(n) = A000005(n)-A161840(n), n >= 1. (End)