A062100 Triangular numbers with every digit a triangular number.

0, 1, 3, 6, 10, 36, 66, 136, 300, 630, 666, 3003, 3160, 10011, 13366, 16110, 60031, 66066, 106030, 163306, 303031, 333336, 336610, 600060, 630003, 1010331, 1030330, 1063611, 1313010, 3306306, 3316600, 6601161, 10006101, 11066160, 13336030, 16310616, 30330366

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

Cf. A000217.

Sequence in context: A066245 A356977 A068821 * A262242 A339783 A317361

Adjacent sequences: A062097 A062098 A062099 * A062101 A062102 A062103

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