%I #16 Mar 22 2020 23:43:01

%S 7,87,312,1287,10572,81103,397212,881912,5270652,7601169,134021535,

%T 421518419,1402775027,4204494972,42305694389,397212509427,

%U 1943649189427,6130065071251

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

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TriangularNumber.html">Triangular Number</a>

%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]] > i, nsmall[[n0]] = i]];

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

%Y Cf. A036525, A048355-A049364.

%K nonn,base,more

%O 1,1

%A _Patrick De Geest_, Mar 15 1999

%E a(13)-a(15) from _Lars Blomberg_, May 16 2011

%E a(16)-a(18) from _Giovanni Resta_, Oct 30 2019