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A115939 Numbers k such that the k-th triangular number contains each of the 10 decimal digits exactly once. 2
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 (list; graph; refs; listen; history; text; internal format)
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 A190882 A251278

Adjacent sequences:  A115936 A115937 A115938 * A115940 A115941 A115942

KEYWORD

nonn,base,fini,full

AUTHOR

Giovanni Resta, Feb 06 2006

STATUS

approved

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Last modified October 16 20:36 EDT 2021. Contains 348047 sequences. (Running on oeis4.)