let rec summ5 x =
let stringList = [x.ToString() ; "second string"]
String.concat "<sep>" stringList
let res = summ5 "argument"
printfn "%s" res
bGV0IHJlYyBzdW1tNSB4ID0gCiBsZXQgc3RyaW5nTGlzdCA9IFt4LlRvU3RyaW5nKCkgOyAic2Vjb25kIHN0cmluZyJdCiBTdHJpbmcuY29uY2F0ICI8c2VwPiIgc3RyaW5nTGlzdAoKbGV0IHJlcyA9ICBzdW1tNSAiYXJndW1lbnQiCnByaW50Zm4gIiVzIiByZXMK