A119208 - OEIS

A119208

Triangular numbers composed of digits {4,5,9}.

45, 55, 595, 5995, 49455, 55945, 594595, 5559445, 555594445, 9955945495, 55555944445, 95444955595, 5555559444445, 9545454599955, 499594959455595, 549999555454495, 555555594444445, 55555555944444445, 5555555559444444445, 5999995494459499455

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

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

Giovanni Resta, Tridigital Triangular Numbers.

FORMULA

a(n) = A000217(A119209(n)). - Tyler Busby, Mar 25 2023

MATHEMATICA

Select[Flatten[Table[FromDigits/@Tuples[{4, 5, 9}, n], {n, 17}]], OddQ[ Sqrt[ 8#+1]]&] (* The program will take a long time to run. *) (* Harvey P. Dale, May 23 2021 *)

CROSSREFS

Cf. A000217, A053955, A119209. See A119033 for a table of cross-references.

Sequence in context: A116247 A168108 A037042 * A068812 A119071 A119158

Adjacent sequences: A119205 A119206 A119207 * A119209 A119210 A119211

KEYWORD

nonn,base

AUTHOR

Giovanni Resta, May 10 2006

EXTENSIONS

a(19)-a(20) from Tyler Busby, Mar 25 2023

STATUS

approved