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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
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
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.)