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A279430 Numbers k such that k^2 has an odd number of digits in base 2 and the middle digit is 0. 14
0, 2, 4, 5, 8, 9, 10, 16, 17, 18, 19, 22, 32, 33, 34, 35, 36, 37, 40, 41, 44, 64, 65, 66, 67, 68, 69, 70, 71, 76, 77, 80, 81, 84, 85, 87, 90, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 144, 145, 146, 147, 151, 152, 153, 156, 157, 160, 161, 164 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Lars Blomberg, Table of n, a(n) for n = 1..10000

Andrew Weimholt, Middle digit in square numbers, Seqfan Mailing list, Dec 12 2016.

MATHEMATICA

a[n_]:=Part[IntegerDigits[n, 2], (Length[IntegerDigits[n, 2]]+1)/2];

Select[Range[0, 164], OddQ[Length[IntegerDigits[#^2, 2]]] && a[#^2]==0 &] (* Indranil Ghosh, Mar 06 2017 *)

PROG

(PARI) isok(k) = my(d=digits(k^2, 2)); (#d%2 == 1) && (d[#d\2 +1] == 0);

for(k=0, 164, if(k==0 || isok(k)==1, print1(k, ", "))); \\ Indranil Ghosh, Mar 06 2017

(Python)

i=0

j=1

while i<=164:

....n=str(bin(i**2)[2:])

....l=len(n)

....if l%2==1 and n[(l-1)/2]=="0":

........print (str(i))+", ",

........j+=1

....i+=1 # Indranil Ghosh, Mar 06 2017

CROSSREFS

Cf. A279431.

See A279420-A279429 for a base-10 version.

Sequence in context: A045702 A005658 A166021 * A003714 A010402 A010443

Adjacent sequences:  A279427 A279428 A279429 * A279431 A279432 A279433

KEYWORD

nonn,base,easy

AUTHOR

Lars Blomberg, Jan 07 2017

STATUS

approved

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Last modified February 18 20:32 EST 2018. Contains 299330 sequences. (Running on oeis4.)