OFFSET
1,1
COMMENTS
These numbers are related to amicable pairs of the form (G * pq, G * rs), where G is coprime to pq and rs. The interesting case of G=2^n is shown in A180330.
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
EXAMPLE
For pq = 33 = 3*11, the corresponding rs is 35 because (3+1)(11+1) = 48 = (5+1)(7+1).
MATHEMATICA
nn=1000; sp=Select[Range[3, 4*nn/3, 2], Last/@FactorInteger[ # ]=={1, 1}&]; prods=Table[Times@@(1+First/@FactorInteger[n]), {n, sp}]; dups=Select[Tally[prods], #[[2]]>1&]; goodProds=Sort[Transpose[dups][[1]]]; pos=Select[Range[Length[sp]], sp[[ # ]]<=nn && MemberQ[goodProds, prods[[ # ]]]&]; sp[[pos]]
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Sep 07 2010
STATUS
approved