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 A292786 a(n) = psi(n) - phi(n). 4
 0, 2, 2, 4, 2, 10, 2, 8, 6, 14, 2, 20, 2, 18, 16, 16, 2, 30, 2, 28, 20, 26, 2, 40, 10, 30, 18, 36, 2, 64, 2, 32, 28, 38, 24, 60, 2, 42, 32, 56, 2, 84, 2, 52, 48, 50, 2, 80, 14, 70, 40, 60, 2, 90, 32, 72, 44, 62, 2, 128, 2, 66, 60, 64, 36, 124, 2, 76, 52, 120, 2, 120, 2, 78, 80, 84, 36, 144 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Even numbers that are not the terms of this sequence are 12, 102, 114, 130, ... LINKS Antti Karttunen, Table of n, a(n) for n = 1..65537 FORMULA a(n) = A001615(n) - A000010(n). a(n) = 2 iff n is prime. a(n) = 2*A069359(n) iff n is not in A000977. MATHEMATICA psi[n_] := If[n < 1, 0, n Sum[ MoebiusMu[d]^2/d, {d, Divisors@ n}]]; Array[psi@# - EulerPhi@# &, 87] (* Robert G. Wilson v, Sep 23 2017 *) PROG (PARI) a001615(n) = my(f=factor(n)); prod(i=1, #f~, f[i, 1]^f[i, 2] + f[i, 1]^(f[i, 2]-1)); a(n) = a001615(n) - eulerphi(n); \\ after Charles R Greathouse IV at A001615 CROSSREFS Cf. A000010, A001615, A051612, A069359, A291784. Sequence in context: A322671 A087909 A076078 * A326486 A357817 A053204 Adjacent sequences: A292783 A292784 A292785 * A292787 A292788 A292789 KEYWORD nonn,easy,look AUTHOR Altug Alkan, Sep 23 2017 STATUS approved

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Last modified February 3 21:17 EST 2023. Contains 360045 sequences. (Running on oeis4.)