A231431 Evil squares.

0, 9, 36, 144, 169, 225, 441, 576, 676, 729, 900, 1369, 1764, 2025, 2209, 2304, 2704, 2809, 2916, 3249, 3600, 3721, 3969, 4761, 5329, 5476, 6561, 6889, 7056, 8100, 8649, 8836, 9216, 9801, 10816, 11025, 11236, 11449, 11664, 11881, 12321, 12996, 13225, 14161, 14400, 14884, 15129, 15876, 17689, 18769, 19044, 19881, 21316, 21904

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 20 2013

Keywords

• nonn
• base
• easy

Comments

Numbers n^2 such that A159918(n) is even.

Intersection of A000290 and A001969.

Examples

			36 is in the sequence because 36 = 6^2 and 36 in base 2 is 100100, having an even number of 1's.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000290, A125498.

Programs

Mathematica

Select[Range[0,150]^2,EvenQ[DigitCount[#,2,1]]&] (* Harvey P. Dale, Nov 23 2015 *)

PARI

is(n)=hammingweight(n)%2==0 && issquare(n) \\ Charles R Greathouse IV, Nov 20 2013

Formula

Conjecture: a(n) ~ 4n^2. - Charles R Greathouse IV, Nov 20 2013

Extensions

Corrected and extended by Harvey P. Dale, Nov 23 2015