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A159081
Let d be the largest element of A008578 which divides n, then a(n) is the position of d in A008578.
1
1, 2, 3, 2, 4, 3, 5, 2, 3, 4, 6, 3, 7, 5, 4, 2, 8, 3, 9, 4, 5, 6, 10, 3, 4, 7, 3, 5, 11, 4, 12, 2, 6, 8, 5, 3, 13, 9, 7, 4, 14, 5, 15, 6, 4, 10, 16, 3, 5, 4, 8, 7, 17, 3, 6, 5, 9, 11, 18, 4, 19, 12, 5, 2, 7, 6, 20, 8, 10, 5, 21, 3, 22, 13, 4, 9, 6, 7, 23, 4, 3, 14, 24, 5, 8, 15, 11, 6, 25, 4, 7, 10, 12
OFFSET
1,2
COMMENTS
Let p be the largest prime factor of n; if p = prime(k) then set a(n) = k + 1. a(n) = A061395(n) + 1.
FORMULA
a(n) = A049084(A006530(n)) + 1. A008578(a(n)) = A006530(n);
EXAMPLE
For n=30, the largest element of the set {1,2,3,5} (1 and prime divisors of 30) is 5, and 5 is a(n)=4th term of A008578, the extended set of primes.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Apr 05 2009
EXTENSIONS
Edited by R. J. Mathar, Apr 06 2009
Correction for change of offset in A158611 and A008578 in Aug 2009 Jaroslav Krizek, Jan 27 2010
STATUS
approved