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 A129335 a(n) = phi(n!!) where phi is the Euler totient function. In other words, a(n) = A000010(A006882(n)). 0
 1, 1, 2, 4, 8, 16, 48, 128, 432, 1024, 4320, 12288, 51840, 147456, 777600, 2359296, 12441600, 42467328, 223948800, 849346560, 4702924800, 16986931200, 103464345600, 407686348800, 2586608640000, 9784472371200, 69838433280000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS FORMULA If n>2 is prime, a(n) = (n-1)*a(n-2). If n=2*p, where p is odd prime, a(n)=(n-2)*a(n-2). Otherwise, a(n) = n*a(n-2). - Max Alekseyev, May 26 2007 MATHEMATICA Table[EulerPhi[n!! ], {n, 1, 30}] (* Stefan Steinerberger, May 30 2007 *) CROSSREFS Cf. A006882, A048855. Sequence in context: A289671 A096853 A027155 * A264635 A046237 A013084 Adjacent sequences:  A129332 A129333 A129334 * A129336 A129337 A129338 KEYWORD nonn AUTHOR Leroy Quet, May 26 2007 EXTENSIONS More terms from Stefan Steinerberger, May 30 2007 STATUS approved

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Last modified August 20 19:51 EDT 2019. Contains 326155 sequences. (Running on oeis4.)