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A231431 Evil squares. 6
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified April 16 17:01 EDT 2021. Contains 343050 sequences. (Running on oeis4.)