A048535 a(n) is the smallest value of m such that A002378(m), the m-th oblong number, contains exactly n 3's.

5, 36, 182, 1817, 4830, 5773, 153079, 577355, 3659694, 18366636, 182574188, 576484036, 1839384036, 17701331569, 36542213005, 485935528988, 1814754484036, 5755287250288, 5773506159694, 182738579159694, 230940107675430, 1820173984357898, 18202838331788627, 57475066797119386, 182305878493709942

Offset: 1

Author

Patrick De Geest, May 15 1999

Keywords

• nonn
• base

Examples

			From _Jesse Sealand_, Oct 05 2019: (Start)
a(1) = 5 since A002378(5) = 30;
a(2) = 36 since A002378(36) = 1332;
a(3) = 182 since A002378(182) = 33306;
a(4) = 1817 since A002378(1817) = 3303306, etc.
(End)
		

Links

• Eric Weisstein's World of Mathematics, Pronic Number

Crossrefs

Cf. A048536, A002378 (oblong numbers).

Cf. A048529, A048531, A048533, A048537, A048539, A048541, A048543, A048545, A048547.

Programs

Mathematica

With[{s = 2 Accumulate[Range[0, 10^6]]}, Table[-1 + FirstPosition[s, ?(DigitCount[#, 10, 3] == n &)][[1]], {n, 8}]] (* _Michael De Vlieger, Oct 05 2019 *)

Extensions

a(13)-a(16) from Lars Blomberg, Jun 10 2011

Name edited by Jesse Sealand, Oct 05 2019

a(17) from Giovanni Resta, Oct 09 2019

a(18)-a(25) from Max Alekseyev, Jul 25 2024