28.5 Power if only 10 or 20 can be tested.

power.anova.test(groups = 3,
                 between.var = var(means),
                 within.var = mean(sds*sds),
                 sig.level = .05, power = NULL,
                 n = 10)

## 
##      Balanced one-way analysis of variance power calculation 
## 
##          groups = 3
##               n = 10
##     between.var = 476
##      within.var = 1210
##       sig.level = 0.05
##           power = 0.66
## 
## NOTE: n is number in each group

Note this is likely underpowered

power.anova.test(groups = 3,
                 between.var = var(means),
                 within.var = mean(sds*sds),
                 sig.level = .05, power = NULL,
                 n = 20)

## 
##      Balanced one-way analysis of variance power calculation 
## 
##          groups = 3
##               n = 20
##     between.var = 476
##      within.var = 1210
##       sig.level = 0.05
##           power = 0.94
## 
## NOTE: n is number in each group

Note this is likely acceptable