A341712 - OEIS

%I #19 May 12 2022 14:04:09

%S 3,12,39,112,292,710,1629,3567,7505,15266,30140,57983,108981,200625,

%T 362433,643653,1125269,1939149,3297411,5538254,9195371,15104245,

%U 24561098,39562657,63160404,99987453,157029090,244754385,378754786,582124254,888874067,1348842728

%N a(n) = A120963(2*n)/2.

%C A bisection of A341710.

%p with(numtheory):

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

%p g:= proc(n) option remember; `if`(n=0, 1, add(

%p       g(n-j)*add(d*b(d), d=divisors(j)), j=1..n)/n)

%p     end:

%p a:= n-> g(2*n)/2:

%p seq(a(n), n=1..40);  # _Alois P. Heinz_, Feb 19 2021

%t terms = 64; (* number of terms of A120963 *)

%t nmax = Floor[terms/2];

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

%t      {k, 1, m*terms}] + O[x]^(terms+1), x];

%t S[m = 1];

%t S[m++];

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

%t A120963 = S[m];

%t a[n_ /; 1 <= n <= nmax] := A120963[[2n+1]]/2;

%t Table[a[n], {n, 1, nmax}] (* _Jean-François Alcover_, May 12 2022 *)

%Y Cf. A120963, A341710, A341711.

%K nonn

%O 1,1

%A _N. J. A. Sloane_, Feb 19 2021