A118389 Least triangular number T(k) that contains the consecutive digits of n, where T(k) = k*(k+1)/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

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 A349873

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