Recaman Sequence

.block

license: mit

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index.html

  <script src="https://d3js.org/d3.v5.min.js"></script>

  <svg width="960" height="500"></svg>
<script>
  var n = 60;

  var curr = 0;
  var seq = [curr];

  for (var i = 1; i < n; i++) {
    var next = curr - i;

    if (next < 0 || seq.includes(next)) {
      curr = curr + i;
      seq.push(curr);
    } else {
      curr = next;
      seq.push(next);
    }
  }

  console.log(seq);

  var data = [];
  var sign = 1;

  for (var i = 0; i < n - 1; i++) {
    var center = (seq[i] + seq[i+1]) / 2;
    var radius = Math.abs(seq[i] - seq[i+1]) / 2;
    var dir = Math.sign(seq[i+1] - seq[i]);
    data.push({center: center, radius: radius, sign: sign, dir: dir});
    sign = -sign;
  }

  console.log(data);

  var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height"),
    g = svg.append("g");

  var x = d3.scaleLinear().range([0, width]).domain([0, d3.max(seq)])

  var arc = d3.arc()
      .innerRadius(function(d) { return x(d.radius)})
      .outerRadius(function(d) { return x(d.radius)})
      .endAngle(function(d) { return d.dir * d.sign * (Math.PI / 2) + (d.sign - 1) * Math.PI/2})
      .startAngle(function(d) { return -d.dir * d.sign * (Math.PI /2) + (d.sign - 1) * Math.PI/2});

  var DURATION = 300;

    g.selectAll('path')
    .data(data)
    .enter()
    .append('path')
     .attr("stroke", "steelblue")
      .attr("stroke-width", "2")
     .attr("d", arc)
     .attr("transform", function(d) { return "translate(" + x(d.center) + ",240)"})
     .attr("stroke-dasharray", function(d) { return this.getTotalLength() + ", " + this.getTotalLength(); })
     .attr("stroke-dashoffset", function(d) { return this.getTotalLength(); })
     .transition()
        .delay(function(d, i) { return i *  DURATION;})
        .duration(DURATION * 2)
        .ease(d3.easeLinear)
        .attr("stroke-dashoffset", 0);




  </script> 

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