A272897 Largest prime factor of n-th taxi-cab number A001235(n).

19, 19, 19, 43, 19, 13, 43, 19, 37, 79, 19, 19, 79, 79, 43, 61, 79, 127, 19, 19, 13, 43, 109, 19, 37, 139, 43, 19, 37, 31, 79, 43, 19, 139, 127, 127, 13, 19, 19, 61, 103, 151, 409, 73, 181, 13, 277, 79, 43, 79, 79, 19, 43, 139, 61, 19, 61, 79, 103, 127, 19, 37, 79, 163, 79, 19, 19

Offset: 1

Author

Altug Alkan, May 09 2016

Keywords

• nonn

Comments

There are two versions of "taxicab numbers" that are A001235 and A011541. This sequence focuses on the version A001235.

All terms of this sequence are members of this sequence infinitely many times. For example, in this sequence there are infinitely many times "277" and there are infinitely many times "17".

Is a(n) >= 13 for all n? This is true for n <= 10000. - Robert Israel, May 09 2016

Examples

			a(1) = A006530(A001235(1)) = A006530(1729) = 19.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001235, A006530.

Programs

Mathematica

FactorInteger[Select[Range[2*10^5], Length[PowersRepresentations[#, 2, 3]] > 1 &]][[All, -1, 1]] (* Michael De Vlieger, May 10 2016, after Harvey P. Dale at A001235 *)

Formula

a(n) = A006530(A001235(n)).