A280649 Numbers k such that k^3 has an odd number of digits and the middle digit is 9.

28, 33, 41, 108, 132, 157, 159, 175, 178, 181, 184, 187, 190, 193, 196, 204, 207, 209, 466, 474, 480, 486, 492, 508, 514, 515, 518, 519, 528, 536, 539, 552, 570, 588, 611, 627, 638, 648, 651, 657, 658, 659, 660, 706, 707, 708, 714, 719, 745, 757, 763, 765, 772

Offset

1,1

Comments

The sequence of cubes starts: 21952, 35937, 68921, 1259712, 2299968, 3869893, 4019679, 5359375, ...

Links

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

Jeremy Gardiner, Middle digit in cube numbers, Seqfan Mailing list, Dec 12 2016.

Example

28^3 = 21(9)52, 181^3 = 592(9)741, 536^3 = 1539(9)0656.

Mathematica

ond9Q[n_]:=Module[{idn=IntegerDigits[n^3], len}, len=Length[idn]; OddQ[len]&&idn[[(len+1)/2]]==9]; Select[Range[800], ond9Q] (* Harvey P. Dale, Mar 14 2018 *)

Crossrefs

Cf. A280640-A280648, A181354.

See A279420-A279429 for a k^2 version.

See A279430-A279431 for a k^2 version in base 2.

Sequence in context: A230855 A090637 A261113 * A134657 A261106 A138687

Adjacent sequences: A280646 A280647 A280648 * A280650 A280651 A280652

Keyword

nonn,base,easy

Author

Lars Blomberg, Jan 07 2017

Status

approved