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A122444
Greatest prime factor of powers of semiprimes.
2
1, 2, 3, 3, 5, 7, 5, 2, 7, 11, 5, 13, 11, 17, 7, 3, 19, 13, 23, 7, 17, 11, 19, 29, 31, 2, 13, 23, 37, 11, 3, 41, 17, 43, 29, 13, 31, 47, 19, 5, 53, 37, 23, 59, 17, 11, 61, 41, 43, 19, 67, 47, 71, 13, 29, 73, 31, 79, 53, 23, 83
OFFSET
1,2
COMMENTS
A122443 is least prime factor of powers of semiprimes. Cf. A076397 Largest prime factor of n-th perfect power.
LINKS
FORMULA
a(n) = A006530(A085155(n)) = greatest prime factor of A085155 powers of semiprimes.
MATHEMATICA
FactorInteger[#][[-1, 1]] & /@ Select[Range@ 168, Function[n, Or[n == 1, And[Length@ # == 1, EvenQ@ First@ #], And[Length@ # == 2, SameQ @@ #]] &[FactorInteger[n][[All, -1]]]]] (* Michael De Vlieger, Mar 04 2017 *)
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Sep 06 2006
STATUS
approved