spikar

simulate <- function(nsim,nvec){
  simdx <- c()
  for(i in 1:length(nvec)) 
    simdx <- c(simdx,rep(1:nsim,each=nvec[i])+(i-1)*nsim)
  dt <- data.table(sim=simdx)
  bigN <- nrow(dt)
  dt$n <- rep(rep(nvec,nvec),each=nsim)
  dt$one <- 1
  dt$simc <- dt[,cumsum(one),by=sim]$V1
  dt$one <- NULL