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A238984 a(n+1) is the product of the last three digits of the sequence up to a(n), start with a(0)=2. 6
2, 8, 32, 48, 64, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48, 192, 18, 16, 48 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
Additional rule: if there are fewer than k=3 digits in the sequence so far, then it is "extended to the left" with the first digit (i.e., that digit is repeated as often as necessary).
For any starting value, the sequence obtained through these rules ends either in repeating 0's, or in repeating 1's, or in the cycle (16,48,192,18). So 2 is the least starting value for which this nontrivial cycle is entered, after 5 iterations, at a(5)=192.
LINKS
FORMULA
a(n+4)=a(n) for n > 4.
EXAMPLE
a(1) = 2*2*2 = 8 (here the initial digit is used 3 times), a(2) = 2*2*8 = 32 (here the initial digit is used twice to get k=3 factors), a(3) = 8*3*2 = 48, ...
PROG
(PARI) A238984(n, a=2, k=3, print_all=0)={my(L=if(a, digits(a), [0]), S=Str(-k"..")); while(#L<k, L=concat(L[1], L)); for(m=1, n, print_all&&print1(a", "); a=prod(i=1, k, L[i]); L=vecextract(concat(L, if(a, digits(a))), S)); a}
CROSSREFS
Sequence in context: A071387 A330782 A200063 * A071389 A026369 A269818
KEYWORD
nonn,base
AUTHOR
Eric Angelini and M. F. Hasler, Aug 01 2014
EXTENSIONS
PARI program corrected by Jens Kruse Andersen, Aug 02 2014
STATUS
approved

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Last modified July 12 12:19 EDT 2024. Contains 374247 sequences. (Running on oeis4.)