A115939 - OEIS

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

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OFFSET

1,1

COMMENTS

There are 82 such numbers, the largest being 138959.

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

LINKS

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

EXAMPLE

T(75555) = 2854316790.

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 *)

CROSSREFS

Cf. A000217, A115940, A118668.

Sequence in context: A223368 A061405 A061529 * A168630 A361035 A190882

Adjacent sequences: A115936 A115937 A115938 * A115940 A115941 A115942

KEYWORD

nonn,base,fini,full

AUTHOR

Giovanni Resta, Feb 06 2006

STATUS

approved