A280643 Numbers k such that k^3 has an odd number of digits and the middle digit is 3.

29, 34, 39, 46, 118, 125, 141, 142, 155, 161, 170, 211, 213, 477, 489, 511, 522, 526, 529, 535, 554, 573, 582, 586, 589, 631, 632, 633, 645, 663, 680, 691, 699, 723, 733, 744, 747, 770, 785, 790, 816, 817, 832, 854, 859, 863, 869, 873, 878, 892, 897, 901, 923

Offset

1,1

Comments

The sequence of cubes starts: 24389, 39304, 59319, 97336, 1643032, 1953125, 2803221, 2863288, ...

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

29^3 = 24(3)89, 161^3 = 417(3)281, 663^3 = 2914(3)4247.

Mathematica

Select[Range[925], OddQ[len=Length[IntegerDigits[#^3]]]&&Part[IntegerDigits[#^3], (len+1)/2]==3 &] (* Stefano Spezia, Oct 03 2023 *)

Crossrefs

Cf. A280640-A280642, A280644-A280649, A181354.

See A279420-A279429 for a k^2 version.

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

Sequence in context: A295153 A031172 A159022 * A102527 A039307 A043130

Adjacent sequences: A280640 A280641 A280642 * A280644 A280645 A280646

Keyword

nonn,base,easy

Author

Lars Blomberg, Jan 07 2017

Status

approved