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A122839 Numbers such that Sigma(m)*UnitarySigma(m)= k*UnitaryPhi(m)^2, for some integer k. 2
1, 2, 3, 6, 14, 15, 30, 35, 42, 60, 70, 78, 105, 190, 210, 312, 357, 418, 570, 714, 910, 1045, 1254, 1428, 2090, 2730, 3135, 3640, 4522, 4674, 5278, 6270, 10659, 10920, 12441, 13566, 14630, 15834, 16770, 18696, 20026, 21318, 23374, 24871, 24882, 24969, 25070, 25714, 27170 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Terms which are squarefree appear on A121556.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..1000

MAPLE

isA122839 := proc(m)

    A047994(m) ;

    modp(numtheory[sigma](m)*A034448(m), %^2) = 0 ;

end proc:

for m from 1 do

    if isA122839(m) then

        printf("%a, \n", m) ;

    end if;

end do: # R. J. Mathar, Sep 04 2018

MATHEMATICA

f[p_, e_] := (p^(e+1)-1)*(p^e+1)/(p-1)/(p^e-1)^2; seqQ[1] = True; seqQ[n_] := IntegerQ [Times @@ (f @@@ FactorInteger[n])]; Select[Range[27170], seqQ] (* Amiram Eldar, Dec 11 2019 *)

PROG

(PARI) isok(m) = ((sigma(m)*usigma(m)) % uphi(m)^2) == 0; \\ Michel Marcus, Jan 24 2019

CROSSREFS

Cf. A000203, A034448, A047994, A121556.

Sequence in context: A134737 A030733 A335288 * A258077 A121556 A123041

Adjacent sequences:  A122836 A122837 A122838 * A122840 A122841 A122842

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto, Oct 23 2006

EXTENSIONS

More terms from Michel Marcus, Jan 24 2019

STATUS

approved

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Last modified March 4 07:04 EST 2021. Contains 341781 sequences. (Running on oeis4.)