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A069903 Number of distinct prime factors of n-th triangular number. 6
0, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 3, 3, 2, 2, 2, 3, 4, 3, 2, 3, 3, 2, 2, 3, 3, 3, 3, 2, 3, 3, 3, 4, 3, 2, 3, 4, 3, 3, 3, 3, 4, 3, 2, 3, 3, 2, 3, 4, 3, 2, 3, 4, 4, 3, 2, 4, 4, 2, 3, 3, 3, 4, 3, 3, 4, 4, 3, 3, 3, 2, 3, 4, 4, 4, 3, 3, 3, 2, 2, 4, 5, 3, 3, 4, 3, 3, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = A001221(A000217(n)).

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

A000217(11) = 11*(11+1)/2 = 66 = 2*3*11, therefore a(11) = 3.

MATHEMATICA

PrimeNu[#]&/@Accumulate[Range[90]] (* Harvey P. Dale, Oct 06 2016 *)

CROSSREFS

Cf. A069901, A069902, A069904.

Sequence in context: A272231 A209253 A165113 * A331003 A086007 A108582

Adjacent sequences:  A069900 A069901 A069902 * A069904 A069905 A069906

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Apr 10, 2002

STATUS

approved

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Last modified April 6 21:24 EDT 2020. Contains 333286 sequences. (Running on oeis4.)