OFFSET
1,2
LINKS
Giovanni Resta, Tridigital Triangular Numbers
FORMULA
MATHEMATICA
Rest[Select[FromDigits/@Tuples[{0, 1, 4}, 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, 4} where t is n*(n+1) div 2]; // Vincenzo Librandi, Dec 18 2015
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, May 10 2006
EXTENSIONS
a(17) from Tyler Busby, Mar 27 2023
STATUS
approved