cp's OEIS Frontend

A006715 Describe the previous term! (method A - initial term is 3).

%I A006715 M2965 #52 Feb 16 2025 08:32:30
%S A006715 3,13,1113,3113,132113,1113122113,311311222113,13211321322113,
%T A006715 1113122113121113222113,31131122211311123113322113,
%U A006715 132113213221133112132123222113,11131221131211132221232112111312111213322113,31131122211311123113321112131221123113111231121123222113
%N A006715 Describe the previous term! (method A - initial term is 3).
%C A006715 Method A = 'frequency' followed by 'digit'-indication.
%C A006715 a(n+1) - a(n) is divisible by 10^5 for n > 5. - _Altug Alkan_, Dec 04 2015
%D A006715 S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 452-455.
%D A006715 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%D A006715 I. Vardi, Computational Recreations in Mathematica. Addison-Wesley, Redwood City, CA, 1991, p. 4.
%H A006715 T. D. Noe, <a href="/A006715/b006715.txt">Table of n, a(n) for n=1..20</a>
%H A006715 Éric Brier, Rémi Géraud-Stewart, David Naccache, Alessandro Pacco, and Emanuele Troiani, <a href="https://arxiv.org/abs/2006.06837">Stuttering Conway Sequences Are Still Conway Sequences</a>, arXiv:2006.06837 [math.DS], 2020.
%H A006715 Éric Brier, Rémi Géraud-Stewart, David Naccache, Alessandro Pacco, and Emanuele Troiani, <a href="https://arxiv.org/abs/2006.07246">The Look-and-Say The Biggest Sequence Eventually Cycles</a>, arXiv:2006.07246 [math.DS], 2020.
%H A006715 J. H. Conway, <a href="http://dx.doi.org/10.1007/978-1-4612-4808-8_53">The weird and wonderful chemistry of audioactive decay</a>, in T. M. Cover and Gopinath, eds., Open Problems in Communication and Computation, Springer, NY 1987, pp. 173-188.
%H A006715 S. R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/constant/cnwy/cnwy.html">Conway's Constant</a> [Broken link]
%H A006715 S. R. Finch, <a href="http://web.archive.org/web/20010207194413 /http://www.mathsoft.com/asolve/constant/cnwy/cnwy.html">Conway's Constant</a> [From the Wayback Machine]
%H A006715 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a>.
%e A006715 The term after 3113 is obtained by saying "one 3, two 1's, one 3", which gives 132113.
%t A006715 RunLengthEncode[ x_List ] := (Through[ {First, Length}[ #1 ] ] &) /@ Split[ x ]; LookAndSay[ n_, d_:1 ] := NestList[ Flatten[ Reverse /@ RunLengthEncode[ # ] ] &, {d}, n - 1 ]; F[ n_ ] := LookAndSay[ n, 3 ][ [ n ] ]; Table[ FromDigits[ F[ n ] ], {n, 11} ] (* _Zerinvary Lajos_, Mar 21 2007 *)
%o A006715 (Perl)
%o A006715 # This outputs the first n elements of the sequence, where n is given on the command line.
%o A006715 $s = 3;
%o A006715 for (2..shift @ARGV) {
%o A006715     print "$s, ";
%o A006715     $s =~ s/(.)\1*/(length $&).$1/eg;
%o A006715 }
%o A006715 print "$s\n";
%o A006715 ## Arne 'Timwi' Heizmann (timwi(AT)gmx.net), Mar 12 2008
%Y A006715 Cf. A001140, A001141, A001143, A001145, A001151, A001154, A001155, A005150, A006751.
%Y A006715 Cf. A088204 (continuous version).
%K A006715 nonn,base,easy,nice
%O A006715 1,1
%A A006715 _N. J. A. Sloane_