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 A036518 Smallest triangular number containing exactly n 1's. 1
 1, 171, 1711, 105111, 1188111, 18111171, 1111160511, 11161151121, 111111101310, 11311511141161, 121111912011111, 11111811011411671, 11101111131911151, 11111111111113201, 111111312111373411111, 1119711111215111121171, 111112117111126711111195, 1141011111112731111616111 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA a(n) = A000217(A048356(n)). - Michel Marcus, Aug 12 2014 MAPLE P := proc(q, h) local a, b, c, k, n; c:=0; for n from 1 to q do a:=0; b:=n*(n+1)/2; for k from 1 to ilog10(n*(n+1)/2)+1 do if (b mod 10)=h then a:=a+1; fi; b:=trunc(b/10); od; if a>c then c:=a; print(n*(n+1)/2); fi; od; end: P(10^9, 1); # Paolo P. Lava, Aug 08 2014 MATHEMATICA nsmall = Table[Infinity, 20]; For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i];   n0 = Count[IntegerDigits[p], 1];   If[nsmall[[n0]] > p, nsmall[[n0]] = p]]; ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *) CROSSREFS Cf. A048356, A036517-A036526. Sequence in context: A220869 A251329 A221754 * A187133 A185838 A199902 Adjacent sequences:  A036515 A036516 A036517 * A036519 A036520 A036521 KEYWORD nonn,base AUTHOR EXTENSIONS Definition clarified by Robert Israel, Aug 10 2014 a(15)-a(16) from A048356 by Michel Marcus, Aug 12 2014 a(17)-a(18) from Giovanni Resta, Oct 30 2019 STATUS approved

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Last modified December 2 06:44 EST 2020. Contains 338868 sequences. (Running on oeis4.)