A264646 A simple self-describing sequence S: n concatenated with the n-th digit of S.

11, 21, 32, 41, 53, 62, 74, 81, 95, 103, 116, 122, 137, 144, 158, 161, 179, 185, 191, 200, 213, 221, 231, 246, 251, 262, 272, 281, 293, 307, 311, 324, 334, 341, 355, 368, 371, 386, 391, 401, 417, 429, 431, 448, 455, 461, 479, 481, 492, 500, 510, 522, 531

Offset

1,1

Comments

Although A003602 and this sequence initially agree in their digit-streams, they differ after 48 digits. - N. J. A. Sloane, Nov 20 2015

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Éric Angelini, n concatenated with the nth digit of S, SeqFan list, Nov 19 2015.

Example

.   n |  1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10  | 11  | 12  | 13  | 14
. ----+----+---+---+---+---+---+---+---+---+-----+-----+-----+-----+-----
. a(n)| 11  21  32  41  53  62  74  81  95  103   116   122   137   144
. digs| 1 1 2 1 3 2 4 1 5 3 6 2 7 4 8 1 9 5 1 0 3 1 1 6 1 2 2 1 3 7 1 4 4 .

Prog

(Haskell)
import Data.List (genericIndex)
a264646 n = a264646_list !! (n-1)
a264646_list = 11 : f 2 [0, 1, 1] where
   f x digs = (foldl (\v d -> 10 * v + d) 0 ys) : f (x + 1) (digs ++ ys)
     where ys = map (read . return) (show x) ++ [genericIndex digs x]
(Python)
from itertools import count, islice
def agen(): # generator of terms
    an, s = 11, [None, 1, 1]
    for n in count(2):
        yield an
        an = 10*n + s[n]
        s.extend(list(map(int, str(an))))
print(list(islice(agen(), 53))) # Michael S. Branicky, Oct 03 2024

Crossrefs

Cf. A003602.

Sequence in context: A239464 A180105 A288186 * A139113 A109335 A086982

Adjacent sequences: A264643 A264644 A264645 * A264647 A264648 A264649

Keyword

nonn,base

Author

Eric Angelini and Reinhard Zumkeller, Nov 20 2015

Status

approved