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A071312
Squarefree numbers k such that the largest prime factor of k is equal to the sum of the other prime factors of k.
2
30, 70, 286, 646, 1798, 3135, 3526, 3570, 6279, 7198, 8855, 8970, 10366, 10626, 10695, 11571, 16095, 16530, 17255, 17391, 20615, 20706, 20735, 20806, 23326, 24738, 24882, 26691, 28083, 31031, 36519, 36890, 38086, 38130, 41151, 41615
OFFSET
1,1
COMMENTS
If k = p(1)*p(2)*...p(r) is in the sequence, where p(r) is the largest prime factor, then p(r) = p(1)+p(2)+...+p(r-1).
LINKS
EXAMPLE
20706 = 2*3*7*17*29 and 2+3+7+17 = 29 hence 20706 is in the sequence.
MATHEMATICA
Select[Range[40000], SquareFreeQ[#] && Plus @@ (f = FactorInteger[#][[;; , 1]]) == 2 * f[[-1]] &] (* Amiram Eldar, Apr 23 2022 *)
PROG
(PARI) for(n=2, 100000, if(issquarefree(n)*sum(i=1, omega(n)-1, component(component(factor(n), 1), i))==vecmax(factor(n, 1)), print1(n, ", ")))
CROSSREFS
Sequence in context: A301900 A357854 A071141 * A071142 A218327 A259753
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Jun 11 2002
STATUS
approved