A068093 Smallest n-digit triangular number.

1, 10, 105, 1035, 10011, 100128, 1000405, 10001628, 100005153, 1000006281, 10000020331, 100000404505, 1000001326005, 10000002437316, 100000012392316, 1000000042485480, 10000000037150046, 100000000000018810, 1000000000179470703, 10000000002237948990

Offset

1,2

Links

Table of n, a(n) for n=1..20.

Formula

Triangular number with index given by A068092.

Mathematica

triInverse[n_] := Floor[(Sqrt[1 + 8*n] - 1)/2]; tri[n_] := n*(n+1)/2; Table[tri[1 + triInverse[10^(n-1) - 1]], {n, 20}] (* T. D. Noe, Jul 27 2012 *)

Crossrefs

Cf. A068092, A068094, A095863, A095864, A095865, A095866.

Sequence in context: A300850 A360276 A210136 * A260214 A077369 A068618

Adjacent sequences: A068090 A068091 A068092 * A068094 A068095 A068096

Keyword

base,easy,nonn

Author

Amarnath Murthy, Feb 19 2002

Extensions

More terms from Sascha Kurz, Mar 06 2002

Status

approved