login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A119039 Triangular numbers composed of digits {0,1,5}. 2
1, 10, 15, 55, 105, 5050, 5151, 10011, 15051, 105111, 500500, 501501, 505515, 510555, 10015050, 50005000, 50015001, 50055015, 50105055, 51010050, 51111105, 51151555, 110551015, 1051501011, 1505550501, 5000050000, 5000150001, 5000550015, 5001050055, 5010055050 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..30.

G. Resta, Tridigital Triangular Numbers

MATHEMATICA

Rest[Select[FromDigits/@Tuples[{0, 1, 5}, 12], IntegerQ[(Sqrt[8 # + 1] - 1)/2] &]] (* Vincenzo Librandi, Dec 18 2015 *)

PROG

(MAGMA) [t: n in [1..2*10^7] | Set(Intseq(t)) subset {0, 1, 5} where t is n*(n+1) div 2]; // Vincenzo Librandi, Dec 18 2015

CROSSREFS

Cf. A000217, A058416, A119040. See A119033 for a table of cross-references.

Sequence in context: A188651 A272307 A092192 * A047189 A278921 A035407

Adjacent sequences:  A119036 A119037 A119038 * A119040 A119041 A119042

KEYWORD

nonn,base

AUTHOR

Giovanni Resta, May 10 2006

EXTENSIONS

More terms from Vincenzo Librandi, Dec 18 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 15 06:29 EST 2019. Contains 329144 sequences. (Running on oeis4.)