A280645 Numbers k such that k^3 has an odd number of digits and the middle digit is 5.

26, 43, 107, 109, 119, 122, 136, 139, 144, 150, 177, 179, 197, 203, 205, 472, 476, 494, 499, 501, 506, 510, 523, 537, 555, 561, 563, 568, 583, 603, 608, 629, 636, 649, 664, 694, 696, 726, 752, 753, 762, 766, 769, 780, 795, 796, 807, 814, 819, 826, 831, 845

Offset

1,1

Comments

The sequence of cubes starts: 17576, 79507, 1225043, 1295029, 1685159, 1815848, 2515456, 2685619, ...

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

26^3 = 17(5)76, 150^3 = 337(5)000, 603^3 = 2192(5)6227

Mathematica

Select[Range[900], OddQ[IntegerLength[#^3]]&&IntegerDigits[#^3][[(IntegerLength[ #^3]+1)/2]]==5&] (* Harvey P. Dale, Aug 24 2017 *)

Crossrefs

Cf. A280640-A280644, A280646-A280649, A181354.

See A279420-A279429 for a k^2 version.

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

Sequence in context: A285513 A138727 A248404 * A260207 A130771 A217775

Adjacent sequences: A280642 A280643 A280644 * A280646 A280647 A280648

Keyword

nonn,base,easy

Author

Lars Blomberg, Jan 07 2017

Status

approved