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A123041 Numbers such that UnitarySigma(m)^2 = k*Sigma(m)*UnitaryPhi(m), for some integer k. 2
1, 2, 3, 6, 14, 15, 30, 35, 42, 70, 78, 105, 190, 210, 357, 418, 570, 714, 910, 1045, 1254, 1976, 2090, 2730, 3135, 4522, 4674, 5278, 5412, 5928, 6270, 8580, 10659, 12441, 12628, 13566, 14630, 15834, 16770, 17220, 20026, 21318, 23374, 24871, 24882 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Terms which are squarefree appear on A121556.

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

PROG

(PARI) A047994(n)={ local(i, resul, rmax); if(n==1, return(1) ); i=factor(n); rmax=matsize(i)[1]; resul=1; for(r=1, rmax, resul *= i[r, 1]^i[r, 2]-1; ); return(resul); }

A034448(n)={ sumdiv(n, d, if(gcd(d, n/d)==1, d)) }

isA123041(n)={ local(s); s=(A034448(n))^2; if( s % (sigma(n)*A047994(n)) == 0, return(s/sigma(n)/A047994(n)), return(0) ); }

{ for(n=1, 30000, k=isA123041(n); if( k, print1(n, ", ") ); ); } \\ R. J. Mathar, Sep 27 2006

CROSSREFS

Cf. A123042, A121556, A034448, A047994.

Sequence in context: A122839 A258077 A121556 * A078557 A005537 A306600

Adjacent sequences:  A123038 A123039 A123040 * A123042 A123043 A123044

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto, Sep 24 2006

EXTENSIONS

More terms from R. J. Mathar, Sep 27 2006

STATUS

approved

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Last modified December 15 20:00 EST 2019. Contains 330000 sequences. (Running on oeis4.)