title: Keras explanation: number of nodes in input layer
body: <p>I'm trying to understand the relationship between a simple <em>Perceptron</em> and a neural network one gets when using the keras <em>Sequence</em> class.</p>
  
  <p>I learned that the neural network perceptron looks as such:</p>
  
  <p><a href="https://i.stack.imgur.com/P1DQq.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/P1DQq.png" alt="enter image description here"></a> </p>
  
  <p>Each "node" in the first layer is one of the features of a sample x_1, x_2,...,x_n</p>
  
  <p>Could somebody explain the jump to the neural network I find in the Keras package below?
  Since the input layer has four nodes, does that mean that network consists of four of the perceptron networks?
  <a href="https://i.stack.imgur.com/gctum.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gctum.jpg" alt="enter image description here"></a></p>