How to loop on a list R Error:[[i]] : invalid subscript type 'list'

>head(forecast1)
$`104.csv`
    Point Forecast     Lo 80    Hi 80     Lo 95    Hi 95
104       2.980583 -1.173982 7.135147 -3.373276 9.334441
105       2.980583 -1.173982 7.135147 -3.373276 9.334441
106       2.980583 -1.173982 7.135147 -3.373276 9.334441
107       2.980583 -1.173982 7.135147 -3.373276 9.334441
$`105.csv`
   Point Forecast    Lo 80    Hi 80    Lo 95    Hi 95
37       581.4081 492.1122 670.7041 444.8417 717.9746
38       637.5269 547.9410 727.1128 500.5170 774.5367
39       624.6460 523.2233 726.0688 469.5333 779.7587
40       650.9142 548.1605 753.6679 493.7660 808.0624
class(forecast1)
[1] "list"> sum(unlist(as.vector((forecast1[[1]][4]))))
[1] 11.92233
> sum(unlist(as.vector((forecast1[[2]][4]))))
[1] 2494.495
> sum(unlist(as.vector((forecast1[[3]][4]))))
[1] 544.325

for (i in forecast1){
  sum <- sum(unlist(as.vector((forecast1[[i]][4]))))
 print(sum)
 }
Error in forecast1[[i]] : invalid subscript type 'list'

What is the error of this loop?? Individually the code is working perfect,expected output is a vector with each sum,