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A068071 Triangular number remains triangular when the least significant digit is moved to the beginning. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..30.

EXAMPLE

8911, T133, is in the sequence because 8911 becomes 1891 which is T61.

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}]

CROSSREFS

Cf. A067269.

Sequence in context: A160965 A069708 A061455 * A067269 A071299 A061380

Adjacent sequences:  A068068 A068069 A068070 * A068072 A068073 A068074

KEYWORD

base,nonn

AUTHOR

Robert G. Wilson v, Feb 28 2002

STATUS

approved

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Last modified August 18 04:50 EDT 2019. Contains 326072 sequences. (Running on oeis4.)