def p_a2(npsyns, ninputs):
	"""
	Probability of selecting one input given ninputs and npsyns attempts. This
	uses a binomial distribution.
	
	@param npsyns: The number of proximal synapses.
	
	@param ninputs: The number of inputs.
	
	@return: The computed probability.
	"""
	
	p = 1. / ninputs
	return npsyns * p * ((1 - p) ** (npsyns - 1))