OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
423 is a term since 423 = 3^2 * 47, 423 + 1 = 424 = 2^3 * 53 and 423 + 2 = 425 = 5^2 * 17 all have one unitary prime divisor and one nonunitary prime divisor.
MATHEMATICA
q[n_] := n == 1 || Count[(e = FactorInteger[n][[;; , 2]]), 1] == Length[e]/2; v = q /@ Range[3]; seq = {}; Do[v = Append[Drop[v, 1], q[k]]; If[And @@ v, AppendTo[seq, k - 2]], {k, 4, 10^5}]; seq
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Sep 30 2021
STATUS
approved