A272897 - OEIS

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

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OFFSET

1,1

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

LINKS

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

FORMULA

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

EXAMPLE

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

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 *)

CROSSREFS

Cf. A001235, A006530.

Sequence in context: A010858 A291499 A168525 * A040343 A022353 A323177

Adjacent sequences: A272894 A272895 A272896 * A272898 A272899 A272900

KEYWORD

nonn

AUTHOR

Altug Alkan, May 09 2016

STATUS

approved