A048349 -id:A048349 - cp's OEIS frontend

A048359 a(n) is the index of the smallest triangular number containing exactly n 4's.

9, 94, 537, 1043, 29238, 28790, 94238, 942703, 2967970, 45748113, 170565790, 939618480, 2981759361, 29814031731, 94285146809, 298802358238, 2837045748113, 9428516473384, 29810549959517, 537482082424790, 699205897721757, 2974721655733337, 29032426496744790, 29814339990932029, 1043498506508221519

Offset: 1

Patrick De Geest, Mar 15 1999

Eric Weisstein's World of Mathematics, Triangular Number

Cf. A036521, A048349, A048355, A048356, A048357, A048358, A048360, A048361, A048362, A048363, A048364, A048537.

nsmall = Table[Infinity, 20];
For[i = 0, i <= 10^6, i++, p = PolygonalNumber[i];
  n0 = Count[IntegerDigits[p], 4];
  If[nsmall[[n0]] > i, nsmall[[n0]] = i]];
ReplaceAll[nsmall, Infinity -> "?"] (* Robert Price, Mar 22 2020 *)

a(13)-a(14) from Lars Blomberg, May 13 2011
a(15)-a(18) from Giovanni Resta, Oct 30 2019
a(19)-a(25) from Max Alekseyev, Mar 07 2025

A036511 Smallest square containing exactly n 4's.

Original entry on oeis.org

4, 144, 1444, 44944, 6441444, 47444544, 4434494464, 44424414441, 4243443441444, 44844344414464, 444431244445444, 44044624434444544, 441544444344443449, 14444545446449449444, 346454444084444444644, 44024844440444424044544, 444448493447444044441744

Offset: 1

David W. Wilson

a(21) > 10^28. - Giovanni Resta, Jul 27 2018

Giovanni Resta, Table of n, a(n) for n = 1..20

Cf. A048349. - Jon E. Schoenfield, Jan 24 2009

a[n_] := Block[{k=1}, While[DigitCount[k^2, 10, 4] != n, k++]; k^2]; Array[a, 7] (* Giovanni Resta, Jul 27 2018 *)

a(13)-a(16) from Jon E. Schoenfield, Jan 17 2009

a(17) from Giovanni Resta, Jul 27 2018

cp's OEIS Frontend

A048359 a(n) is the index of the smallest triangular number containing exactly n 4's.

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