OFFSET
1,2
COMMENTS
a(16) > 10^5. - Robert Price, May 22 2018
EXAMPLE
iphi(21) = iphi(22) = 14, thus 21 is in the sequence.
MATHEMATICA
irelprime[n_] := Select[temp = iDivisors[n]; Range[n], Intersection[iDivisors[#], temp] === {1} &]; bitty[k_] := Union[Flatten[Outer[Plus, Sequence @@ {0, #1} & /@ Union[2^Range[0, Floor[Log[2, k]]]*Reverse[IntegerDigits[k, 2]]]]]];
iDivisors[k_Integer] := Sort[(Times @@ (First[it]^(#1 /. z -> List)) &) /@ Flatten[Outer[z, Sequence @@ bitty /@ Last[it = Transpose[FactorInteger[k]]], 1]]]; iDivisors[1] := {1}; iphi[n_] := Length[irelprime[n]]; iphiQ[n_] := iphi[n] == iphi[n + 1]; Select[Range[10^3], iphiQ](* after Wouter Meeussen at A064379 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Mar 28 2018
EXTENSIONS
a(11)-a(15) from Robert Price, May 22 2018
a(16)-a(24) from Amiram Eldar, Mar 26 2023
STATUS
approved