A048531 a(n) is the smallest value of m such that A002378(m), the m-th oblong number, contains exactly n 1's.

3, 10, 105, 1010, 10203, 33928, 105551, 335128, 1054130, 12313046, 100573943, 333192303, 1054092885, 4261585525, 30184681729, 133083117303, 331829837885, 4136557897710, 11666683809854, 105410706823885, 333183899837885, 3333333637837885, 6466156610468989, 33928029520312720, 138242940872632303

Offset: 1

Author

Patrick De Geest, May 15 1999

Keywords

• nonn
• base

Examples

			From _Jesse Sealand_, Oct 06 2019: (Start)
a(1) = 3 since A002378(3) = 12;
a(2) = 10 since A002378(10) = 110;
a(3) = 105 since A002378(105) = 11130;
a(4) = 1010 since A002378(1010) = 1021110, etc.
(End).
		

Links

• Eric Weisstein's World of Mathematics, Pronic Number

Crossrefs

Cf. A048532, A002378.

Cf. A048529, A048533, A048535, A048537, A048539, A048541, A048543, A048545, A048547.

Extensions

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

Name edited by Jesse Sealand, Oct 06 2019

a(17) from Giovanni Resta, Oct 09 2019

a(18)-a(25) from Max Alekseyev, Jul 24 2024