Recaman Sequence in R Demo http://rextester.com/SNJP54298 Source https://www.reddit.com/r/dailyprogrammer/comments/81aexf/weekly_28_mini_challenges/

recaman.png

recaman.R

recaman <- function(n, s=c()) {
  a <- 0

  if (n > 0) {
    val <- recaman(n - 1, s)
    
    a <- val$a
    s <- c(val$s, a)

    an1 <- a - n
    
    if (an1 > -1 && !(an1 %in% s)) {
      # If not in sequence.
      a <- an1
    }
    else {
      # If in sequence.
      a <- a + n
    }
  }

  list(a=a, s=c(s, a))
}

x-client.R

for (i in 1:100) print(recaman(i)$a)

# Visualization
library(ggplot2)

data <- as.data.frame(sapply(1:100, function(a) { recaman(a)$a }))
names(data) <- c('y')
data$x <- as.numeric(row.names(data))

g <- ggplot(data, aes(x=x, y=y, color=y))
g <- g + geom_point(size=2, shape=16)
g <- g + labs(title='Recman Sequence', x='Sequence #', y='Value')
g <- g + scale_color_gradient(low='purple', high='pink')
g <- g + theme(legend.position="none")
g <- g + scale_x_continuous(breaks=c(seq(from=1, to=nrow(data), by=nrow(data)/20), nrow(data)))
g

x-output.txt

      a
1     1
2     3
3     6
4     2
5     7
6    13
7    20
8    12
9    21
10   11
11   22
12   10
13   23
14    9
15   24
16    8
17   25
18   43
19   62
20   42
21   63
22   41
23   18
24   42
25   17
26   43
27   16
28   44
29   15
30   45
31   14
32   46
33   79
34  113
35   78
36  114
37   77
38   39
39   78
40   38
41   79
42   37
43   80
44   36
45   81
46   35
47   82
48   34
49   83
50   33
51   84
52   32
53   85
54   31
55   86
56   30
57   87
58   29
59   88
60   28
61   89
62   27
63   90
64   26
65   91
66  157
67  224
68  156
69  225
70  155
71  226
72  154
73  227
74  153
75  228
76  152
77   75
78  153
79   74
80  154
81   73
82  155
83   72
84  156
85   71
86  157
87   70
88  158
89   69
90  159
91   68
92  160
93   67
94  161
95   66
96  162
97   65
98  163
99   64
100 164