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A045914 Triangular numbers with all digits the same. 14
0, 1, 3, 6, 55, 66, 666 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

A118668(a(n)) = 1. - Reinhard Zumkeller, Jul 11 2015

REFERENCES

D. Ballew and R. Weger, Repdigit triangular numbers, J. Rec. Math. Vol. 8(2), p. 96, 1975-76.

L. E. Dickson, History of the Theory of Numbers, Vol. II, p. 33, Chelsea NY, 1952.

E. B. Escott, Math. Quest. Educational Times, (2) 8 (1905), 33-34. - N. J. A. Sloane, Mar 31 2014

Bir Kafle et al., Triangular repblocks, Fib. Q., 56:4 (2018), 325-328.

LINKS

Table of n, a(n) for n=1..7.

MATHEMATICA

Select[Union[Flatten[Table[FromDigits[PadRight[{}, n, k]], {n, 3}, {k, 0, 9}]]], OddQ[ Sqrt[8#+1]]&] (* Harvey P. Dale, Feb 11 2020 *)

CROSSREFS

Cf. A213516 (triangular numbers having only 1 or 2 different digits).

Cf. A118668.

Sequence in context: A066569 A051641 A003098 * A303351 A067610 A067609

Adjacent sequences:  A045911 A045912 A045913 * A045915 A045916 A045917

KEYWORD

fini,full,nonn,base

AUTHOR

Felice Russo

EXTENSIONS

Added 0 - T. D. Noe, Jun 22 2012

STATUS

approved

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Last modified December 2 14:26 EST 2020. Contains 338877 sequences. (Running on oeis4.)