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A058250
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GCD of n-th primorial number and its totient.
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8
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1, 1, 2, 2, 6, 30, 30, 30, 30, 330, 2310, 2310, 2310, 2310, 2310, 53130, 690690, 20030010, 20030010, 20030010, 20030010, 20030010, 20030010, 821230410, 821230410, 821230410, 821230410, 13960916970, 739928599410, 739928599410
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OFFSET
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0,3
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LINKS
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FORMULA
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EXAMPLE
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a(6) = gcd(30030,5760) = 30.
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MAPLE
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[seq(igcd(product(ithprime(k), k=1..m), product(ithprime(k)-1, k=1..m)), m=1..50)];
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MATHEMATICA
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GCD[#, EulerPhi[#]]&/@Rest[FoldList[Times, 1, Prime[Range[30]]]] (* Harvey P. Dale, Dec 19 2012 *)
Fold[Append[#1, {#1, #2, GCD[#1, #2]} & @@ {#4 #1, #2 (#4 - 1)} & @@ Append[#1[[-1]], #2]] &, {{1, 1, 1}}, Prime@ Range[29]][[All, -1]] (* Michael De Vlieger, Apr 25 2019 *)
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PROG
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(PARI) a(n) = my(pr=prod(k=1, n, prime(k))); gcd(pr, eulerphi(pr)); \\ Michel Marcus, Apr 13 2019
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CROSSREFS
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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