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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.)