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 A104191 Sum of Euler totient function between successive powers of two. 1
 1, 3, 14, 54, 236, 920, 3730, 14862, 59776, 238856, 956110, 3823410, 15299542, 61193632, 244779854, 979111158, 3916558030, 15666093384, 62664665094, 250658276292, 1002634426882, 4010536846838, 16042149531756, 64168594080686, 256674403929154, 1026697590590342, 4106790388347028 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 0..36 FORMULA a(n) = phi(2^n) + phi(2^n + 1) + ... + phi(2^(n+1) - 2) + phi(2^(n+1) - 1). a(n) ~ 4^n * 9/Pi^2. - Charles R Greathouse IV, Sep 05 2017 MATHEMATICA Table[Sum[EulerPhi[i], {i, 2^n, 2^(n + 1) - 1}], {n, 0, 24}] PROG (PARI) a(n)=my(s); forfactored(k=2^n, 2^(n+1)-1, s+=eulerphi(k)); s \\ Charles R Greathouse IV, Sep 05 2017 CROSSREFS Sequence in context: A099487 A179610 A166680 * A151540 A226466 A026544 Adjacent sequences:  A104188 A104189 A104190 * A104192 A104193 A104194 KEYWORD nonn AUTHOR Roger L. Bagula, Mar 12 2005 EXTENSIONS a(20)-a(26) from Charles R Greathouse IV, Sep 05 2017 STATUS approved

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