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 A053196 Cototients of even numbers. 1
 1, 2, 4, 4, 6, 8, 8, 8, 12, 12, 12, 16, 14, 16, 22, 16, 18, 24, 20, 24, 30, 24, 24, 32, 30, 28, 36, 32, 30, 44, 32, 32, 46, 36, 46, 48, 38, 40, 54, 48, 42, 60, 44, 48, 66, 48, 48, 64, 56, 60, 70, 56, 54, 72, 70, 64, 78, 60, 60, 88, 62, 64, 90, 64, 82, 92, 68, 72, 94, 92, 72, 96 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Not all even numbers arise as cototient values: see A005278. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA a(n) = 2n - phi(2n) = A051953(2n). MATHEMATICA Table[(2 n - EulerPhi[2 n]), {n, 1, 80}] (* Vincenzo Librandi, Jul 27 2013 *) PROG (PARI) a(n) = 2*n - eulerphi(2*n) \\ Michel Marcus, Jul 26 2013 (MAGMA) [2*n-EulerPhi(2*n): n in [1..80]]; // Vincenzo Librandi, Jul 28 2013 CROSSREFS Cf. A000010, A051953, A005278. Sequence in context: A246601 A288529 A288772 * A159634 A186690 A002131 Adjacent sequences:  A053193 A053194 A053195 * A053197 A053198 A053199 KEYWORD nonn,easy AUTHOR Labos Elemer, Mar 02 2000 STATUS approved

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Last modified April 18 03:59 EDT 2021. Contains 343072 sequences. (Running on oeis4.)