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A048361 a(n) is the index of the smallest triangular number containing exactly n 6's. 1
3, 11, 36, 363, 3366, 8563, 35963, 394123, 3055048, 11531588, 115464831, 115470036, 1154484036, 10645763163, 35401884036, 152754484036, 365148371588, 2292012515963 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

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], 6];

  If[nsmall[[n0]] > i, nsmall[[n0]] = i]];

ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)

CROSSREFS

Cf. A036523, A048355-A049364.

Sequence in context: A286318 A119054 A119090 * A119161 A119211 A119235

Adjacent sequences:  A048358 A048359 A048360 * A048362 A048363 A048364

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 28 07:19 EDT 2021. Contains 346318 sequences. (Running on oeis4.)