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A118389 Least triangular number T(k) that contains the consecutive digits of n, where T(k) = k*(k+1)/2. 2
0, 1, 21, 3, 45, 15, 6, 78, 28, 91, 10, 1128, 120, 136, 1431, 15, 1653, 171, 1830, 190, 120, 21, 1225, 231, 2415, 253, 1326, 276, 28, 2926, 300, 231, 325, 3321, 2346, 351, 36, 378, 3828, 3916, 406, 741, 4278, 435, 4465, 45, 465, 4753, 1485, 496, 2850, 351, 528 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The indices, k, of these T(k) for each n are at A118388.

LINKS

T. D. Noe, Table of n, a(n) for n = 0..10000

EXAMPLE

====================

n k T(k)

====================

0 0 0

1 1 1

2 6 21

3 2 3

4 9 45

5 5 15

6 3 6

7 12 78

8 7 28

9 13 91

10 4 10

MATHEMATICA

nn = 68; t = Table[0, {nn}]; n = 0; found = 0; While[found < nn, n++; k = n (n + 1)/2; d = IntegerDigits[k]; s = Sort[FromDigits /@ Flatten[Table[Partition[d, i, 1], {i, Length[d]}], 1]]; i = 1; While[i <= Length[s] && s[[i]] <= nn, If[t[[s[[i]]]] == 0, t[[s[[i]]]] = k; found++]; i++]]; t = Join[{0}, t] (* T. D. Noe, Sep 03 2013 *)

CROSSREFS

Cf. A000217, A118388.

Sequence in context: A040433 A317321 A080472 * A077690 A018855 A263277

Adjacent sequences:  A118386 A118387 A118388 * A118390 A118391 A118392

KEYWORD

base,easy,nonn

AUTHOR

Jonathan Vos Post, Apr 26 2006

EXTENSIONS

Corrected by T. D. Noe, Sep 03 2013

STATUS

approved

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Last modified August 24 03:20 EDT 2019. Contains 326260 sequences. (Running on oeis4.)