A053969 -id:A053969 - cp's OEIS frontend

A119218 Triangular numbers composed of digits {5,6,7}.

6, 55, 66, 666, 5565, 6555, 5656566, 5676765, 6655776, 56567566, 575675766555, 677767555675, 555665666566566, 555667666766556, 5755656755766655, 565767676566675765, 7557657566575767666, 5555555666655656666556566566566

Offset: 1

Giovanni Resta, May 10 2006

a(19) > 10^40. - Tyler Busby, Mar 28 2023

Giovanni Resta, Tridigital Triangular Numbers.

Cf. A000217, A053969, A119219. See A119033 for a table of cross-references.

Select[Flatten[Table[FromDigits/@Tuples[{5,6,7},n],{n,10}]],OddQ[Sqrt[8#+1]]&] (* The program generates the first 10 terms of the sequence. *) (* Harvey P. Dale, Jan 23 2025 *)

a(n) = A000217(A119219(n)). - Michel Marcus, Mar 27 2023

a(18) from Tyler Busby, Mar 28 2023

A053968 Numbers k such that k^2 contains only digits {5,6,7}.

Original entry on oeis.org

24, 26, 76, 869924, 2582184474, 75349689155076, 75879284173334, 815816631091556424, 881854102200458483334, 2562353735836753390526

Offset: 1

Patrick De Geest, Mar 15 2000

P. De Geest, Squares containing at most three distinct digits, Index entries for related sequences
Author?, Source(txt)
H. Mishima, Squares consisted of 3 different digits

Cf. A053969.

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 03 2005
Two more terms from Jon E. Schoenfield, Sep 04 2006
Three more terms from Mishima's website added by Max Alekseyev, May 02 2011

cp's OEIS Frontend

A119218 Triangular numbers composed of digits {5,6,7}.

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