A109879 Numbers n such that n and its digit reversal R(n) both are difference of positive cubes.

7, 19, 91, 127, 721, 919, 999, 1385, 1727, 3159, 4376, 5409, 5831, 6734, 7271, 9045, 9513, 10647, 11824, 12691, 14491, 15967, 16939, 19441, 19621, 25352, 26973, 27872, 28737, 29783, 31213, 35163, 35929, 36153, 37962, 37973, 38656, 38792, 39636

Offset

1,1

Comments

Numbers n such that n and R(n) are both of the form a^3-b^3 with a > b > 0.

Links

Table of n, a(n) for n=1..39.

Example

19 = 3^3 - 2^3 and 91 = 6^3 - 5^3.

Mathematica

t1 = Select[ Union[ Flatten[ Table[n^3 - m^3, {n, 185}, {m, 0, n - 1}]]], # < 10^5 && Mod[ #, 10] != 0 &]; t2 = FromDigits /@ Reverse /@ IntegerDigits /@ t1; Take[ Intersection[t1, t2], 40] (* Robert G. Wilson v, Jul 14 2005 *)

Crossrefs

Cf. A109880.

Sequence in context: A300556 A267378 A088988 * A109880 A363668 A245489

Adjacent sequences: A109876 A109877 A109878 * A109880 A109881 A109882

Keyword

base,nonn

Author

Amarnath Murthy, Jul 10 2005

Extensions

Edited and extended by Robert G. Wilson v, Jul 14 2005

Status

approved