%I #18 Oct 04 2024 06:54:25
%S 11,21,32,41,53,62,74,81,95,103,116,122,137,144,158,161,179,185,191,
%T 200,213,221,231,246,251,262,272,281,293,307,311,324,334,341,355,368,
%U 371,386,391,401,417,429,431,448,455,461,479,481,492,500,510,522,531
%N A simple self-describing sequence S: n concatenated with the n-th digit of S.
%C Although A003602 and this sequence initially agree in their digit-streams, they differ after 48 digits. - _N. J. A. Sloane_, Nov 20 2015
%H Reinhard Zumkeller, <a href="/A264646/b264646.txt">Table of n, a(n) for n = 1..10000</a>
%H Éric Angelini, <a href="http://list.seqfan.eu/oldermail/seqfan/2015-November/015661.html">n concatenated with the nth digit of S</a>, SeqFan list, Nov 19 2015.
%e . n | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14
%e . ----+----+---+---+---+---+---+---+---+---+-----+-----+-----+-----+-----
%e . a(n)| 11 21 32 41 53 62 74 81 95 103 116 122 137 144
%e . 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 .
%o (Haskell)
%o import Data.List (genericIndex)
%o a264646 n = a264646_list !! (n-1)
%o a264646_list = 11 : f 2 [0, 1, 1] where
%o f x digs = (foldl (\v d -> 10 * v + d) 0 ys) : f (x + 1) (digs ++ ys)
%o where ys = map (read . return) (show x) ++ [genericIndex digs x]
%o (Python)
%o from itertools import count, islice
%o def agen(): # generator of terms
%o an, s = 11, [None, 1, 1]
%o for n in count(2):
%o yield an
%o an = 10*n + s[n]
%o s.extend(list(map(int, str(an))))
%o print(list(islice(agen(), 53))) # _Michael S. Branicky_, Oct 03 2024
%Y Cf. A003602.
%K nonn,base
%O 1,1
%A _Eric Angelini_ and _Reinhard Zumkeller_, Nov 20 2015