A119043 - OEIS

A119043

Triangular numbers composed of digits {0,1,7}.

1, 10, 171, 1711, 1770, 10011, 111117701071, 17170010070077710, 101711101707777771, 701000700077010700, 1701111717707771071, 10010107100007777700, 101770070070071771070, 170107111111710707070, 1177170070777107111711, 70071707101001717077017171

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..16.

Giovanni Resta, Tridigital Triangular Numbers.

FORMULA

a(n) = A000217(A119044(n)). - Tyler Busby, Mar 31 2023

MATHEMATICA

Select[FromDigits/@Tuples[{0, 1, 7}, 12], OddQ[Sqrt[8#+1]]&] (* The program generates the first 8 terms of the sequence. *) (* Harvey P. Dale, Sep 06 2022 *)

CROSSREFS

Cf. A000217, A058420, A119044. See A119033 for a table of cross-references.

Sequence in context: A098345 A366299 A361364 * A187204 A346458 A133273

Adjacent sequences: A119040 A119041 A119042 * A119044 A119045 A119046

KEYWORD

nonn,base

AUTHOR

Giovanni Resta, May 10 2006

EXTENSIONS

a(15)-a(16) from Tyler Busby, Mar 22 2023

STATUS

approved