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

312211322212221121123222114, 13112221133211322112211213322114, 312211322212221121123222115, 13112221133211322112211213322115, 312211322212221121123222116, 13112221133211322112211213322116, 312211322212221121123222117, 13112221133211322112211213322117

Offset

1,1

Comments

The transuranic elements Pu=31221132221222112112322211 and Np=1311222113321132211221121332211 are alternating prefixes;

n is suffix of a(2*n - 1) and of a(2*n) in decimal representation.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..500

J. H. Conway, The weird and wonderful chemistry of audioactive decay, in T. M. Cover and Gopinath, eds., Open Problems in Communication and Computation, Springer, NY 1987, pp. 173-188.

Kevin Watkins, Abstract Interpretation Using Laziness: Proving Conway's Lost Cosmological Theorem,

Kevin Watkins, Proving Conway's Lost Cosmological Theorem, POP seminar talk, CMU, Dec 2006

Eric Weisstein's World of Mathematics, Look and Say Sequence

Wikipedia, Look-and-say sequence

Prog

(Haskell)
a215403 n k = a215403_list !! (n-1)
a215403_list = map (foldr (\d v -> 10 * v + d) 0) $
                   concatMap (\x -> map (x :) [plut', nept']) [4..] where
  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]
  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]

Crossrefs

Cf. A119566, A213979.

Sequence in context: A250493 A219322 A280349 * A053776 A217413 A217428

Adjacent sequences: A215400 A215401 A215402 * A215404 A215405 A215406

Keyword

nonn,base

Author

Reinhard Zumkeller, Aug 09 2012

Status

approved