cp's OEIS Frontend

Python

def next_turn(player): # there are players 0 and 1
    global total, position
    ngames = 0
    for i in range(n+1):
        fill = int(column[i]) # height of column i
        if fill < n: # throw a disc into column i
            position = position + 2 ** (i + (n + 1) * fill + ntimesnplus1 * player) # unique identifier for this position
            if position in games: # half of memory and cpu-time can be saved if you exploit symmetry of positions here
                ngames = ngames + games[position]
            else:
                column[i] = column[i] + 1
                total = total + 1
                if position in setfinalpos: # we have reached a known final position
                    ngames = ngames + 1
                else: # check if the new position is a win or if the board is full
                    if check4win(position, player, fill, i) or total == ntimesnplus1:
                        setfinalpos.add(position)
                        ngames = ngames + 1
                    else:
                        numbergames = next_turn(1 - player)
                        ngames = ngames + numbergames
                column[i] = column[i] - 1
                total = total - 1
            position = position - 2 ** (i + (n + 1) * fill + ntimesnplus1 * player)
    games[position] = ngames
    return ngames