OFFSET
1,3
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..200
EXAMPLE
a(6) = 36 is a triangular number, 3 and 6 are also triangular numbers.
MATHEMATICA
Select[FromDigits/@Tuples[{0, 1, 3, 6}, 8], IntegerQ[(Sqrt[8#+1]-1)/2]&] (* Harvey P. Dale, Nov 05 2011 *)
PROG
(PARI) TD(x)= { return(x==0 || x==1 || x==3 || x==6) } { n=t=0; for (m=0, 10^9, t+=m; x=t; td=1; while (x>9, d=x-10*(x\10); if (!TD(d), td=0; break); x\=10); if (td && TD(x), write("b062100.txt", n++, " ", t); if (n==200, break)) ) } \\ Harry J. Smith, Aug 01 2009
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Amarnath Murthy, Jun 16 2001
EXTENSIONS
Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jun 22 2001
Offset corrected by Harry J. Smith, Aug 01 2009
More terms from Harvey P. Dale, Nov 05 2011
STATUS
approved