If you want to retain the dimension names but just not print them, you can define a new print function.
print.matrix <- function(m){
write.table(format(m, justify="right"),
row.names=F, col.names=F, quote=F)
}
> print(mat)
1 3 5 7 9 11 13 15 17 19
2 4 6 8 10 12 14 16 18 20
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