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A048362 a(n) is the index of the smallest triangular number containing exactly n 7's. 1
12, 59, 381, 3684, 8692, 70381, 122292, 3762381, 7453707, 18856074, 124721736, 587838545, 3996943276, 18845571218, 27483805332, 394393554074, 1246890354231, 11642661866667 (list; graph; refs; listen; history; text; internal format)
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
Sequence in context: A167533 A244907 A062477 * A231215 A231340 A099321
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

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Last modified July 14 22:45 EDT 2024. Contains 374323 sequences. (Running on oeis4.)