A119073 Triangular numbers composed of digits {0,4,6}.

6, 66, 406, 666, 66066, 446040, 600060, 46046406, 440466040, 4040600460, 6604444400406, 4440066066400004040, 644006046066000066046, 44464646466606404046664666, 464440406444064040044646006604604066, 660466006640066446666000606004066646, 60404640400640406040004460664400044060

Offset: 1

Author

Giovanni Resta, May 10 2006

Keywords

• nonn
• base

Links

• Giovanni Resta, Tridigital Triangular Numbers.

Crossrefs

Cf. A000217, A058438, A119074.

See A119033 for a table of cross-references.

Programs

Magma

[t: n in [1..2*10^7] | Set(Intseq(t)) subset {0,4,6} where t is n*(n+1) div 2]; // Vincenzo Librandi, Dec 18 2015

Mathematica

Rest[Select[FromDigits/@Tuples[{0, 4, 6}, 10], IntegerQ[(Sqrt[8 # + 1] - 1)/2] &]] (* Vincenzo Librandi, Dec 18 2015 *)

Formula

a(n) = A000217(A119074(n)). - Tyler Busby, Mar 27 2023

Extensions

a(15)-a(16) from Max Alekseyev, May 10 2009

a(17) from Tyler Busby, Mar 27 2023