[seqfan] Re: UnitaryPhi

[zbi74583_boat at yahoo.co.jp]

    Hi  Seqfan
    b(n)  :  The smallest number  m  such that  UnitaryPhi(m) = (n-2)/n*m
    b(n)  :  6, 2, 20, 3, 1008, 4, 72, 5, 4400, 144, 2^10*3^4*5^2*13*31, 7, 2^4*3^3*5^2, 8, 2^4*17, 9, 2^8*3^4*5^2*19, 400,....

    If n=2*k then b(n)=a(k)  If n=2*k+1 and GCD(a(n),a(n-1))=1 then b(n)=a(n)*a(n-1)

    Where a(n)=A318842(n)  The smallest number  m  such that UnitaryPhi(m)=(n-1)/n*m
    The case that n is odd and not(GCD(a(n),a(n-1))=1) is interesting problem
    So  a(15) is the first non trivial term  Next one is a(21)  It is the following
            2^18*3^8*5^3*7^2*31*41*73
    I have tried to compute a(25)  It is unknown



    Yasutoshi