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

1,2

Comments

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

Intersection of A000290 and A001969.

Links

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

Formula

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A000290, A125498.

Sequence in context: A023872 A034557 A285241 * A264515 A002063 A285674

Adjacent sequences: A231428 A231429 A231430 * A231432 A231433 A231434

Keyword

nonn,base,easy

Author

Juri-Stepan Gerasimov, Nov 20 2013

Extensions

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

Status

approved