A122444 Greatest prime factor of powers of semiprimes.

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

Michael De Vlieger, Table of n, a(n) for n = 1..10000

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 *)

Crossrefs

Cf. A000040, A001358, A006530, A020639, A076396, A076397, A085155, A122443.

Sequence in context: A144680 A209702 A077558 * A373751 A066072 A239586

Adjacent sequences: A122441 A122442 A122443 * A122445 A122446 A122447

Keyword

easy,nonn

Author

Jonathan Vos Post, Sep 06 2006

Status

approved