Chart 1.6

  0	      0.24	      0.00
  1	      0.37	      0.24
  2	      0.80	      0.61
  3	      1.38	      1.41
  4	      2.16	      2.79
  5	      3.47	      4.96
  6	      5.47	      8.43
  7	      9.73	     13.90
  8	     12.78	     23.63
  9	     23.84	     36.41
 10	     42.44	     60.24
 11	     70.04	    102.68
 12	     89.49	    172.72
 13	    139.85	    262.21
 14	    185.64	    402.06
 15	    234.70	    587.69
 16	    630.16	    822.39
 17	   1047.30	   1452.55
 18	   1503.17	   2499.85
 19	   2594.07	   4003.02
 20	   2933.61	   6597.09

Chart 1.8

  0	      0.38	      0.00
  1	      0.50	      0.38
  2	      0.92	      0.88
  3	      1.45	      1.79
  4	      3.47	      3.24
  5	      6.83	      6.71
  6	     10.82	     13.55
  7	     23.79	     24.36
  8	     32.55	     48.16
  9	     76.30	     80.70
 10	    139.19	    157.01
 11	    149.74	    296.20
 12	    310.13	    445.93
 13	    565.06	    756.07
 14	   1051.30	   1321.13
 15	   2417.40	   2372.43
 16	   3492.66	   4789.83
 17	   5746.08	   8282.49
 18	  11104.61	  14028.58
 19	  15876.21	  25133.19
 20	  40953.93	  41009.40

Chart 1.9

  0	      0.35	      0.00
  1	      0.57	      0.35
  2	      1.08	      0.91
  3	      1.78	      1.99
  4	      4.51	      3.77
  5	      4.99	      8.28
  6	     10.63	     13.27
  7	     27.33	     23.90
  8	     47.82	     51.23
  9	     75.54	     99.05
 10	    177.57	    174.59
 11	    243.36	    352.16
 12	    703.32	    595.52
 13	   1156.02	   1298.84
 14	   2621.87	   2454.85
 15	   4112.54	   5076.72
 16	  11172.44	   9189.26
 17	  20950.35	  20361.70
 18	  32130.01	  41312.04
 19	  56231.51	  73442.05
 20	  82043.51	 129673.56

retry-chart.py

import random
import sys

min_delay = .2
base = 1.8

def printf(format, *args):
    sys.stdout.write(format % args)

def backoff_time(attempt):
    """Calculate backoff time from minimum delay and attempt number.
    Currently no good reason for choice of backoff, except not to increase too rapidly."""
    return min_delay*base**attempt+random.uniform(0, min_delay*base**attempt)

total = 0

for i in range(21):
    bt = backoff_time(i)
    printf("%3d\t%10.2f\t%10.2f\n", i, round(bt,2), round(total,2))
    total += bt