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A118668 Number of distinct digits needed to write the n-th triangular number in decimal representation. 8
1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 1, 1, 2, 2, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 3, 1, 3, 3, 3, 3, 3, 3, 3, 2, 4, 3, 3, 3, 3, 4, 4, 4, 3, 4, 4, 4, 4, 2, 3, 4, 3, 4, 4, 3, 4, 2, 3, 4, 4, 4, 3, 3, 4, 3, 4, 3, 2, 4, 4, 4, 3, 3, 4, 4, 3, 4, 3, 4, 3, 4, 4, 4, 4, 3, 4, 3, 4, 4, 4, 2, 2, 3, 3, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

0 < a(n) <= 10;

a(n) = A043537(A000217(n)).

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

EXAMPLE

n=99: 99*(99+1)/2 = 4950 -> a(99) = #{0,4,5,9} = 4;

see A119033 for an overview of sequences with terms composed of not more than 3 distinct digits.

n=100: 100*(100+1)/2 = 5050 -> a(100) = #{0,5} = 2;

MATHEMATICA

Length[Union[IntegerDigits[#]]]&/@Accumulate[Range[0, 110]] (* Harvey P. Dale, Jul 23 2012 *)

PROG

(Haskell)

a118668 = a043537 . a000217

a118668_list = map a043537 a000217_list

-- Reinhard Zumkeller, Jul 11 2015

CROSSREFS

Cf. A000217, A043537, A045914, A213517, A213518, A255678.

Sequence in context: A080972 A037814 A179529 * A273429 A273915 A270969

Adjacent sequences:  A118665 A118666 A118667 * A118669 A118670 A118671

KEYWORD

nonn,base

AUTHOR

Reinhard Zumkeller, May 19 2006

STATUS

approved

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Last modified July 31 05:24 EDT 2021. Contains 346367 sequences. (Running on oeis4.)