A133133 - OEIS

%I #10 Jun 02 2021 04:01:26

%S 2,5,7,3,5,11,3,3,2,43,23,59,11,71,73,5,31,7,13,31,5,79,23,83,179,13,

%T 7,109,223,127,2,89,71,97,7,331,7,11,23,409,13,17,47,19,83,109,137,37,

%U 7,577,59,643,19,73,83,683,89,257,97,31,31,7,877,89,53,11,197,7,29,181,11

%N a(n) is the largest prime factor of the sum of the largest prime factors of numbers from 2 to n.

%H Robert Israel, <a href="/A133133/b133133.txt">Table of n, a(n) for n = 2..10000</a>

%e a(11) = gpf(43) = 43;

%e a(12) = gpf(46) = 23.

%p gpf:= proc(n) max(numtheory:-factorset(n)) end proc:

%p map(gpf, ListTools:-PartialSums(map(gpf, [$2..100])));

%o (PARI) gpf(n) = vecmax(factor(n)[,1]);

%o a(n) = gpf(sum(k=2, n, gpf(k))); \\ _Michel Marcus_, Jun 02 2021

%Y Cf. A006530, A088822.

%K easy,nonn,look

%O 2,1

%A Paul Finley (pfinley(AT)touro.edu), Sep 21 2007