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A248128
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Start with a(0)=50, then a(n) = three times the n-th digit of the sequence, for all n > 0.
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4
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50, 15, 0, 3, 15, 0, 9, 3, 15, 0, 27, 9, 3, 15, 0, 6, 21, 27, 9, 3, 15, 0, 18, 6, 3, 6, 21, 27, 9, 3, 15, 0, 3, 24, 18, 9, 18, 6, 3, 6, 21, 27, 9, 3, 15, 0, 9, 6, 12, 3, 24, 27, 3, 24, 18, 9, 18, 6, 3, 6, 21, 27, 9, 3, 15, 0, 27, 18, 3, 6, 9, 6, 12, 6, 21, 9, 6, 12, 3, 24
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OFFSET
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0,1
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COMMENTS
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The terms in between 0's in the sequence converge "from right to left" to a limiting sequence ...,18,6,3,6,21,27,9,3,15,0. This sequence is listed in A248129. Sequence A248130 lists the individual digits, starting from some 0 and going to the left (until another 0 would be reached); they are equal to A248129/3.
It seems natural to use offset 0 to have the initial term equal to a(0) and a(n) directly related to the n-th digit of the sequence.
All terms a(n) with index n>0 are divisible by 3, the sequence a(n)/3 is nothing else than the individual digits of this sequence.
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LINKS
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EXAMPLE
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a(0)=50 by definition, a(1) = 15 = 3*5 (= 3 x the 1st digit of "50"), a(2) = 0 = 3*0 (3 x the 2nd digit of "50,15"), a(3) = 3 = 3*1 (= 3 x the 3rd digit of the sequence which is the 1st digit of a(1) and equals 1).
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PROG
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(PARI) a(n, s=50, d=[])={for(i=1, n, print1(s", "); d=concat(d, if(s, digits(s))); s=3*d[1]; d=vecextract(d, "^1")); s}
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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