OFFSET
1,2
COMMENTS
First odd term greater than 1 is 3234846615. - Robert G. Wilson v, Nov 04 2010
Also numbers n such that A028236(n)/n >= 1. - Klaus Brockhaus, Nov 06 2010
EXAMPLE
a(2) = 30, since 30 = 2*3*5 and 1/2 + 1/3 + 1/5 = 31/30 >= 1.
MATHEMATICA
DeleteCases[ Table[k; A = FactorInteger[k]; If[Sum[1/A[[j]][[1]]^A[[j]][[2]], {j, 1, Length[A]}] >= 1, k, 0], {k, 1, 3900}], 0]
fQ[n_] := Block[{fi = Transpose@ FactorInteger@ n}, Plus @@ (1/(First@fi ^ Last@fi)) >= 1]; Select[Range@ 3900, fQ] (* Robert G. Wilson v, Nov 04 2010 *)
PROG
(Magma) [1] cat [ k: k in [2..4000] | &+[ f[i, 1]^-f[i, 2]: i in [1..#f] ] ge 1 where f is Factorization(k) ]; // Klaus Brockhaus, Nov 06 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
Roberto E. Martinez II, Nov 02 2010, Nov 05 2010
STATUS
approved