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A048363
a(n) is the index of the smallest triangular number containing exactly n 8's.
9
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
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 *)
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