A229236 Palindromic triangular number with palindromic index.

1, 3, 6, 66, 3003, 66066, 617716, 3544453, 6172882716, 30416261403, 61728399382716, 66056806460865066, 3549632679762369453, 354963215686512369453, 30416741529792514761403, 35496321045754012369453, 3041674104186814014761403

Offset: 1

Author

Shyam Sunder Gupta, Sep 17 2013

Keywords

• nonn
• base

Examples

			a(5)=3003 because 3003 is 77th triangular number and 77 is palindrome.
		

Links

• Shyam Sunder Gupta, Table of n, a(n) for n = 1..18

Crossrefs

Cf. A003098, A000217, A008509, A008510.

Programs

Mathematica

Select[Table[{n,(n(n+1))/2},{n,10^8}],AllTrue[#,PalindromeQ]&][[;;,2]] (* Harvey P. Dale, Jun 04 2023 *)

Extensions

Previous Mathematica program replaced by Harvey P. Dale, Jun 04 2023