A068071 Triangular numbers that remain triangular when the least significant digit is moved to the beginning.

1, 3, 6, 10, 55, 66, 210, 253, 666, 780, 4851, 8911, 15400, 17766, 125751, 303810, 407253, 906531, 1125750, 2648451, 5925403, 6706953, 15772536, 22207780, 50085036, 78406503, 438094800, 1623331710, 1764803755, 3437158416

Offset: 1

Author

Robert G. Wilson v, Feb 28 2002

Keywords

• base
• nonn

Examples

			8911 = A000217(133) is in the sequence because 8911 becomes 1891 which is A000217(61).
		

Crossrefs

Cf. A000217, A067269.

Programs

Mathematica

Do[k = FromDigits[ RotateRight[ IntegerDigits[n(n + 1)/2]]]; l = Floor[ Sqrt[2k]]; If[k == l(l + 1)/2, Print[n(n + 1)/2]], {n, 1, 10^5}]