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A120318
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Consecutive refactorable numbers a(n)-1, a(n) in which 11 the smallest prime divisor of a(n).
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0
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..4.
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FORMULA
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a(n) is the first integer of the form (11*k)^(11-1) such that both a(n) and a(n)-1 is refactorable and 11 is the smallest prime divisor of a(n).
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MAPLE
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with(numtheory); RFC11:=[]: p:=ithprime(5): P:=[seq(ithprime(i), i=1..4)]; for w to 1 do for k from 3 to 12^4 by 2 do if andmap(z -> k mod z <> 0, P) then m:=p*k; n:=m^(p-1); t:=tau(n); n1:=n-1; t1:=tau(n1); if (n mod t = 0) and (n1 mod t1 = 0) then RFC11:=[op(RFC11), n]; print(ifactor(n)); fi fi; od od;
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CROSSREFS
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Cf. A033950, A036898, A114617.
Sequence in context: A104319 A003943 A003936 * A095458 A083104 A115531
Adjacent sequences: A120315 A120316 A120317 * A120319 A120320 A120321
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KEYWORD
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nonn
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AUTHOR
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Walter Kehowski, Jun 20 2006
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STATUS
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approved
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