A260214 a(n) is the first triangular number whose decimal representation uses n distinct digits.

0, 10, 105, 1035, 10296, 102378, 1024596, 10348975, 102738945, 1062489753

Offset: 1

Author

Anders Hellström, Jul 19 2015

Keywords

• nonn
• base
• fini
• full

Links

• Anders Hellström, Table of n, a(n) for n = 1..10

Crossrefs

Cf. A000217, A043537, A118668, A255678.

Programs

Mathematica

# (# + 1)/2 & /@ {0, 4, 14, 45, 143, 452, 1431, 4549, 14334, 46097} (* terms in A255678 *) (* Robert G. Wilson v, Jul 21 2015 *)

PARI

number_of_distinct_digits(m) = if(m==0,1,#vecsort(digits(m), , 8))
a(n)=my(m=0); while(!(number_of_distinct_digits(m*(m+1)/2)==n), m++); m*(m+1)/2;
first(m)=vector(m, n, a(n)) \\m<=10 /* Anders Hellström, Aug 03 2015 */

Formula

a(n) = A255678(n)*(A255678(n)+1)/2.