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A085255
Numbers having at least two representations as a sum of two powerful numbers (A001694).
5
17, 33, 36, 40, 41, 50, 52, 57, 65, 68, 72, 73, 76, 80, 81, 85, 89, 97, 104, 108, 109, 113, 116, 117, 125, 129, 130, 132, 133, 136, 137, 144, 145, 148, 152, 153, 157, 160, 164, 170, 172, 177, 180, 185, 189, 193, 197, 200, 201, 204, 205, 208, 209, 216, 221
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Powerful Number.
FORMULA
A085252(a(n)) > 1.
MATHEMATICA
With[{m = 222}, pow = Select[Range[m], # == 1 || Min[FactorInteger[#][[;; , 2]]] > 1 &]; Position[BinCounts[Select[Plus @@@ Union[Sort /@ Tuples[pow, {2}]], # <= m &], {1, m, 1}], _?(# > 1 &)] // Flatten] (* Amiram Eldar, Jan 30 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Jun 23 2003
STATUS
approved