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A069901 Smallest prime factor of n-th triangular number. +0
5
1, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 7, 3, 2, 2, 3, 3, 2, 2, 3, 11, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 19, 3, 2, 2, 3, 3, 2, 2, 3, 23, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 29, 2, 2, 31, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 37, 3, 2, 2, 3, 3, 2, 2, 3, 41, 2, 2, 5, 3, 2, 2 (list; graph; listen)
OFFSET

1,2

COMMENT

a(n) = A020639(A000217(n)).

EXAMPLE

A000217(10) = 10*(10+1)/2 = 55 = 5*11, therefore a(10) = 5.

CROSSREFS

Cf. A069902, A069903, A069904.

Sequence in context: A122028 A049234 A125504 this_sequence A075392 A115039 A032536

Adjacent sequences: A069898 A069899 A069900 this_sequence A069902 A069903 A069904

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Apr 10, 2002

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Last modified July 6 17:22 EDT 2008. Contains 140988 sequences.


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