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A215403 Isotopes of Conway's audioactive transuranic elements, in reversed lexicographic order.

%I A215403 #12 Feb 16 2025 08:33:18
%S A215403 312211322212221121123222114,13112221133211322112211213322114,
%T A215403 312211322212221121123222115,13112221133211322112211213322115,
%U A215403 312211322212221121123222116,13112221133211322112211213322116,312211322212221121123222117,13112221133211322112211213322117
%N A215403 Isotopes of Conway's audioactive transuranic elements, in reversed lexicographic order.
%C A215403 The transuranic elements Pu=31221132221222112112322211 and Np=1311222113321132211221121332211 are alternating prefixes;
%C A215403 n is suffix of a(2*n - 1) and of a(2*n) in decimal representation.
%H A215403 Reinhard Zumkeller, <a href="/A215403/b215403.txt">Table of n, a(n) for n = 1..500</a>
%H A215403 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 A215403 Kevin Watkins, <a href="http://www.cs.cmu.edu/~kw/pubs/conway.pdf">Abstract Interpretation Using Laziness: Proving Conway's Lost Cosmological Theorem, </a>
%H A215403 Kevin Watkins, <a href="http://www.cs.cmu.edu/~kw/pubs/conwayslides.pdf">Proving Conway's Lost Cosmological Theorem, POP seminar talk, CMU, Dec 2006</a>
%H A215403 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LookandSaySequence.html">Look and Say Sequence</a>
%H A215403 Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a>
%o A215403 (Haskell)
%o A215403 a215403 n k = a215403_list !! (n-1)
%o A215403 a215403_list = map (foldr (\d v -> 10 * v + d) 0) $
%o A215403                    concatMap (\x -> map (x :) [plut', nept']) [4..] where
%o A215403   plut' = [1,1,2,2,2,3,2,1,1,2,1,1,2,2,2,1,2,2,2,3,1,1,2,2,1,3]
%o A215403   nept' = [1,1,2,2,3,3,1,2,1,1,2,2,1,1,2,2,3,1,1,2,3,3,1,1,2,2,2,1,1,3,1]
%Y A215403 Cf. A119566, A213979.
%K A215403 nonn,base
%O A215403 1,1
%A A215403 _Reinhard Zumkeller_, Aug 09 2012