A036520 Smallest triangular number containing exactly n 3's.

3, 3003, 33153, 3303735, 333336, 333039336, 13333363350, 330335331336, 3033333513330, 303313733373336, 30333330330333465, 313631353332333336, 330332337333331336, 3333043333303433331, 3333333330453337336653, 30733333373333335323321, 330332334339335333331336, 33033333933433336339893330

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Mathematica

nsmall = Table[Infinity, 20];
For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i];
  n0 = Count[IntegerDigits[p], 3];
  If[nsmall[[n0]] > p, nsmall[[n0]] = p]];
ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)

Crossrefs

Cf. A048358, A036517-A036526.

Sequence in context: A003534 A202520 A281928 * A359130 A193447 A134909

Adjacent sequences: A036517 A036518 A036519 * A036521 A036522 A036523

Keyword

nonn,base

Author

David W. Wilson

Extensions

a(12)-a(18) from Giovanni Resta, Oct 30 2019

Status

approved