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Smallest triangular number containing exactly n 8's.
2

%I #12 Mar 22 2020 17:30:39

%S 28,3828,48828,828828,55888878,3288888856,78888885078,388884828828,

%T 13889888887878,28888888883865,8980885988888880,88838888988888990,

%U 983888888888812878,8838888986888887878,894885888888885888855,78888888822845888188878,1888886085781088888888878,18788848888888828885888126

%N Smallest triangular number containing exactly n 8's.

%t nsmall = Table[Infinity, 20];

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

%t n0 = Count[IntegerDigits[p], 8];

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

%t ReplaceAll[nsmall, Infinity -> "?"] (* _Robert Price_, Mar 22 2020 *)

%Y Cf. A048363, A036517-A036526.

%K nonn,base

%O 1,1

%A _David W. Wilson_

%E a(13)-a(18) from _Giovanni Resta_, Oct 30 2019