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