A115939 Numbers k such that the k-th triangular number contains each of the 10 decimal digits exactly once.

46097, 49796, 50139, 55151, 55484, 56520, 58050, 62495, 62567, 62900, 66294, 68805, 69542, 70766, 72594, 73737, 73971, 74168, 74357, 75555, 76364, 77805, 78686, 78848, 84555, 85959, 86076, 87263, 87669, 88406, 89883, 90287, 90297

Offset: 1

Author

Giovanni Resta, Feb 06 2006

Keywords

• nonn
• base
• fini
• full

Comments

There are 82 such numbers, the largest being 138959.

A118668(a(n)) = 10. - Reinhard Zumkeller, Jul 11 2015

Examples

			T(75555) = 2854316790.
		

Links

• Zak Seidov, Table of n, a(n) for n = 1..82 (full sequence)

Crossrefs

Cf. A000217, A115940, A118668.

Programs

Mathematica

Select[Range[141000], Sort[IntegerDigits[# (# + 1)/2]] == Range[0, 9] &] (* Giovanni Resta, Mar 19 2013 *)
(Sqrt[8#+1]-1)/2&/@Select[FromDigits/@Select[Permutations[Range[0,9]], #[[1]]>0&],OddQ[Sqrt[8#+1]]&] (* Harvey P. Dale, Sep 19 2016 *)