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], 7];
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(13)-a(15) from Lars Blomberg, May 16 2011
a(16)-a(18) from Giovanni Resta, Oct 30 2019
STATUS
approved