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 A110401 a(1) = 999, a(n) is the number obtained by concatenating product of neighboring digits of the previous term. 0
 999, 8181, 888, 6464, 242424, 88888, 64646464, 24242424242424, 8888888888888, 646464646464646464646464, 2424242424242424242424242424242424242424242424, 888888888888888888888888888888888888888888888 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If one uses any other number as a(1), the sequence either comes to an end with a single-digit term or eventually contains increasing strings of 8, 64 and 24 repeatedly. E.g., a(1) = 1234 gives 1234, 2612, 1262, 21212, 2222, 444, 1616, 666, 3636, 181818, 88888, 64646464, 24242424242424, 8888888888888, ... LINKS Table of n, a(n) for n=1..12. PROG (PARI) f(n) = my(d=digits(n), nd=[]); for (k=1, #d-1, nd = concat(nd, digits(d[k]*d[k+1]))); fromdigits(nd); a(n) = if (n==1, 999, f(a(n-1))); \\ Michel Marcus, Dec 08 2018 CROSSREFS Sequence in context: A226752 A043527 A117720 * A213156 A164813 A164814 Adjacent sequences: A110398 A110399 A110400 * A110402 A110403 A110404 KEYWORD base,easy,nonn AUTHOR Amarnath Murthy, Jul 29 2005 EXTENSIONS Corrected and extended by Joshua Zucker, May 10 2006 Edited by Jon E. Schoenfield, Dec 08 2018 STATUS approved

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Last modified April 13 01:59 EDT 2024. Contains 371639 sequences. (Running on oeis4.)