The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A280651 Numbers k such that k^3 has an odd number of digits in base 2 and the middle digit is 1. 2
 1, 5, 7, 11, 18, 19, 20, 26, 27, 28, 41, 42, 45, 47, 49, 66, 67, 69, 70, 71, 72, 73, 74, 75, 76, 77, 103, 106, 110, 111, 113, 115, 119, 120, 122, 123, 124, 125, 126, 162, 164, 165, 166, 168, 171, 177, 178, 180, 181, 182, 184, 185, 190, 194, 197, 199, 201, 259 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Lars Blomberg, Table of n, a(n) for n = 1..10000 EXAMPLE 5^3 = 111(1)101_2, 28^3 = 1010101(1)1000000_2, 111^3 = 1010011011(1)1001001111_2. MATHEMATICA a[n_]:=Part[IntegerDigits[n, 2], (Length[IntegerDigits[n, 2]]+1)/2]; Select[Range[0, 259], OddQ[Length[IntegerDigits[#^3, 2]]] && a[#^3]==1 &] (* Indranil Ghosh, Mar 06 2017 *) ond2Q[n_]:=Module[{idn=IntegerDigits[n^3, 2], len}, len=Length[idn]; OddQ[ len] && idn[[(len+1)/2]]==1]; Select[Range[300], ond2Q] (* Harvey P. Dale, Jul 21 2021 *) PROG (PARI) isok(k) = my(d=digits(k^3, 2)); (#d%2 == 1) && (d[#d\2 +1] == 1); for(k=0, 259, if(isok(k)==1, print1(k, ", "))); \\ Indranil Ghosh, Mar 06 2017 (Python) i=0 j=1 while i<=259: ....n=str(bin(i**3)[2:]) ....l=len(n) ....if l%2==1 and n[(l-1)/2]=="1": ........print (str(i))+", ", ........j+=1 ....i+=1 # Indranil Ghosh, Mar 06 2017 CROSSREFS Cf. A280650. See A279430-A279431 for a k^2 version. See A280640-A280649 for a base-10 version. See A279420-A279429 for a k^2, base-10 version. Sequence in context: A106954 A027755 A260828 * A089785 A226383 A118386 Adjacent sequences:  A280648 A280649 A280650 * A280652 A280653 A280654 KEYWORD nonn,base,easy AUTHOR Lars Blomberg, Jan 12 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 20 11:16 EDT 2022. Contains 353871 sequences. (Running on oeis4.)