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A048358
a(n) is the index of the smallest triangular number containing exactly n 3's.
1
2, 77, 257, 2570, 816, 25808, 163299, 812816, 2463060, 24629808, 246306030, 791999183, 812812816, 2581876578, 81649658057, 247924719918, 812812812816, 8128140492564
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], 3];
If[nsmall[[n0]] > i, nsmall[[n0]] = i]];
ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Patrick De Geest, Mar 15 1999
EXTENSIONS
a(12) corrected by Lars Blomberg, May 13 2011
a(13)-a(15) from Lars Blomberg, May 13 2011
a(16)-a(18) from Giovanni Resta, Oct 30 2019
STATUS
approved