A036522 - OEIS

A036522

Smallest triangular number containing exactly n 5's.

15, 55, 5565, 255255, 12552555, 585555531, 5355555765, 50525595555, 5258558551555, 555595555515, 1551745755555555, 39355555555552515, 552550545955255555, 13555559555595513555, 455557505555605555585, 5555558514557555255755, 555457555855555784555355, 505555585555455555505395

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..18.

MATHEMATICA

nsmall = Table[Infinity, 20];

For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i];

n0 = Count[IntegerDigits[p], 5];

If[nsmall[[n0]] > p, nsmall[[n0]] = p]];

ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)

CROSSREFS