OFFSET
1,2
COMMENTS
Numbers k such that A001414(k) is a perfect square. - Michel Lagneau, May 28 2012
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(2) = 14 because 14 = 2*7 and 2 + 7 = 3^2.
MAPLE
A:= proc(n) local e, j; e := ifactors(n)[2]: add (e[j][1]*e[j][2], j=1..nops(e)) end:
for m from 1 to 1000 do: m2:=sqrt(A(m)):if m2=floor(m2) then printf(`%d, `, m):else fi:od: # Michel Lagneau, May 28 2012
# second Maple program:
q:= n-> issqr(add(i[1]*i[2], i=ifactors(n)[2])):
select(q, [$1..1000])[]; # Alois P. Heinz, Jan 24 2021
MATHEMATICA
lst = {}; Do[ww = Transpose[FactorInteger[k]]; w = ww[[1]].ww[[2]]; If[IntegerQ[Sqrt[w]], AppendTo[lst, k]], {k, 1, 1000}]; lst (* Michel Lagneau, May 28 2012 *)
Select[Range[700], IntegerQ[Sqrt[Total[Flatten[Table[#[[1]], #[[2]]]&/@ FactorInteger[ #]]]]]&] (* Harvey P. Dale, Dec 12 2018 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Joe K. Crump (joecr(AT)carolina.rr.com)
EXTENSIONS
More terms from James A. Sellers, Sep 08 2000
STATUS
approved