A068094 Number of n-digit triangular numbers.

3, 10, 31, 96, 306, 967, 3058, 9670, 30579, 96700, 305793, 967000, 3057922, 9670000, 30579224, 96699996, 305792239, 966999967, 3057922393, 9669999669, 30579223926, 96699996687, 305792239263, 966999966873, 3057922392627, 9669999668731, 30579223926265

Offset

1,1

Links

Table of n, a(n) for n=1..27.

Formula

Differences of successive terms of A068092.

Mathematica

triInverse[n_] := Floor[(Sqrt[1 + 8*n] - 1)/2]; Differences[Table[triInverse[10^(n - 1) - 1], {n, 30}]] (* T. D. Noe, Jul 27 2012 *)

Crossrefs

Cf. A068092, A068093, A095863, A095864, A095865, A095866.

Sequence in context: A363780 A055217 A097472 * A100058 A002160 A214839

Adjacent sequences: A068091 A068092 A068093 * A068095 A068096 A068097

Keyword

base,easy,nonn

Author

Amarnath Murthy, Feb 19 2002

Extensions

More terms from Sascha Kurz, Mar 06 2002

Status

approved