A048363 a(n) is the index of the smallest triangular number containing exactly n 8's.

7, 87, 312, 1287, 10572, 81103, 397212, 881912, 5270652, 7601169, 134021535, 421518419, 1402775027, 4204494972, 42305694389, 397212509427, 1943649189427, 6130065071251, 76024844477168, 98844816642745, 1333325833012312, 6069248534849827, 13303299356842428, 191199837283345112, 1084811955030810572

Offset

1,1

Links

Table of n, a(n) for n=1..25.

Eric Weisstein's World of Mathematics, Triangular Number

Mathematica

nsmall = Table[Infinity, 20];
For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i];
  n0 = Count[IntegerDigits[p], 8];
  If[nsmall[[n0]] > i, nsmall[[n0]] = i]];
ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)

Crossrefs

Cf. A036525, A048353, A048355, A048356, A048357, A048358, A048359, A048360, A048361, A048362, A048364, A048545.

Sequence in context: A346987 A381089 A092586 * A254473 A183613 A295036

Adjacent sequences: A048360 A048361 A048362 * A048364 A048365 A048366

Keyword

nonn,base,changed

Author

Patrick De Geest, Mar 15 1999

Extensions

a(13)-a(15) from Lars Blomberg, May 16 2011

a(16)-a(18) from Giovanni Resta, Oct 30 2019

a(19)-a(25) from Max Alekseyev, Mar 07 2025

Status

approved