A341712 a(n) = A120963(2*n)/2.

3, 12, 39, 112, 292, 710, 1629, 3567, 7505, 15266, 30140, 57983, 108981, 200625, 362433, 643653, 1125269, 1939149, 3297411, 5538254, 9195371, 15104245, 24561098, 39562657, 63160404, 99987453, 157029090, 244754385, 378754786, 582124254, 888874067, 1348842728

Offset: 1

Author

N. J. A. Sloane, Feb 19 2021

Keywords

• nonn

Comments

A bisection of A341710.

Crossrefs

Cf. A120963, A341710, A341711.

Programs

Maple

with(numtheory):
b:= proc(n) option remember; nops(invphi(n)) end:
g:= proc(n) option remember; `if`(n=0, 1, add(
      g(n-j)*add(d*b(d), d=divisors(j)), j=1..n)/n)
    end:
a:= n-> g(2*n)/2:
seq(a(n), n=1..40);  # Alois P. Heinz, Feb 19 2021

Mathematica

terms = 64; (* number of terms of A120963 *)
nmax = Floor[terms/2];
S[m_] := S[m] = CoefficientList[Product[1/(1 - x^EulerPhi[k]),
     {k, 1, m*terms}] + O[x]^(terms+1), x];
S[m = 1];
S[m++];
While[S[m] != S[m-1], m++];
A120963 = S[m];
a[n_ /; 1 <= n <= nmax] := A120963[[2n+1]]/2;
Table[a[n], {n, 1, nmax}] (* Jean-François Alcover, May 12 2022 *)