OFFSET
1,1
COMMENTS
Are there any other terms like 418 that are not in A228562?
No other terms below 2*10^10. - Max Alekseyev, Dec 15 2023
MATHEMATICA
Select[Range[30000], CompositeQ[#] && Not[IntegerQ[Sqrt[#]]] && Not[IntegerQ[#^(1/3)]] && Mod[Binomial[2*#, #], #] == 2 &] (* Vaclav Kotesovec, Oct 17 2019 *)
PROG
(PARI) forcomposite(c=1, , if(!setintersect(Set(isprimepower(c)), [2, 3]), if(Mod(binomial(2*c, c), c)==2, print1(c, ", "))))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Felix Fröhlich, Oct 17 2019
EXTENSIONS
a(4) from Max Alekseyev, Dec 15 2023
STATUS
approved