> [discussing how c(list(1, 2, 3), LETTERS[1:5]) is not what the author would expect] To get list(1, 2, 3, LETTERS[1:5]), you must do something like x <- list(1, 2, 3); x[[4]] <- LETTERS[1:5].

The following works and it looks quite natural:

c(list(1, 2, 3), list(LETTERS[1:5]))