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A341710 a(n) = A120963(n)/2. 3
1, 3, 5, 12, 19, 39, 59, 112, 165, 292, 419, 710, 1001, 1629, 2257, 3567, 4877, 7505, 10133, 15266, 20399, 30140, 39881, 57983, 76085, 108981, 141877, 200625, 259373, 362433, 465493, 643653, 821813, 1125269, 1428725, 1939149, 2449573, 3297411, 4145249, 5538254 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..40.

MAPLE

with(numtheory):

b:= proc(n) option remember; nops(invphi(n)) end:

a:= proc(n) option remember; `if`(n=0, 1/2, add(

      a(n-j)*add(d*b(d), d=divisors(j)), j=1..n)/n)

    end:

seq(a(n), n=1..40);  # Alois P. Heinz, Feb 19 2021

MATHEMATICA

terms = 40;

S[m_] := S[m] = CoefficientList[Product[1/(1 - x^EulerPhi[k]),

     {k, 1, m*terms}] + O[x]^(terms+1), x]/2 // Rest;

S[m = 1];

S[m++];

While[S[m] != S[m-1], m++];

S[m] (* Jean-Fran├žois Alcover, May 12 2022 *)

CROSSREFS

Cf. A120963, A341711, A341712.

Sequence in context: A323866 A082740 A010067 * A024458 A143643 A321679

Adjacent sequences:  A341707 A341708 A341709 * A341711 A341712 A341713

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 19 2021.

STATUS

approved

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Last modified September 25 16:40 EDT 2022. Contains 356986 sequences. (Running on oeis4.)