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A079543
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Numbers n such that n has at least two distinct prime factors and if a prime p divides n then (p-1)|(n-1) and (p+1)|(n+1).
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1
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OFFSET
| 1,1
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COMMENTS
| 2*10^11 < a(8) <= 429079903231. a(9) <= 634061169071. a(10) <= 1199462890625. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 09 2010]
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EXAMPLE
| a(1) = 74431 = 7^4 * 31 because 6 and 30 divide 74430 and 8 and 32 divide 74432.
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MATHEMATICA
| Do[ f = Transpose[ FactorInteger[n]][[1]]; If[ Length[f] > 1 && Union[ Mod[n - 1, f - 1]] == {0} && Union[ Mod[n + 1, f + 1]] == {0}, Print[n]], {n, 6, 10^10}]
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CROSSREFS
| Intersection of A056729 and A080062.
Sequence in context: A172703 A186835 A122065 * A033450 A033448 A058415
Adjacent sequences: A079540 A079541 A079542 * A079544 A079545 A079546
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KEYWORD
| nonn
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AUTHOR
| Don Reble (djr(AT)nk.ca), Jan 22 2003
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EXTENSIONS
| a(6)-a(7) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Apr 09 2010
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