A361151 a(n) = K(n-1) + K(n) + K(n+1), where K(n) = A341711(floor(n/2)).

2, 7, 11, 29, 43, 97, 137, 283, 389, 749, 1003, 1839, 2421, 4259, 5515, 9391, 12011, 19887, 25143, 40665, 50931, 80679, 100161, 155847, 192051, 294047, 359839, 543127, 660623, 984239, 1190359, 1752799, 2109119, 3072351, 3679263, 5307023, 6327871, 9044395

Offset

0,1

Links

Table of n, a(n) for n=0..37.

Example

n=4: 5+19+19 = 43 = a(4).

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-> add(g(2*floor((i+n)/2)+1)/2, i=-1..1):
seq(a(n), n=0..40);  # Alois P. Heinz, Mar 02 2023

Mathematica

nmax1 = 40;
terms = nmax1 + 2; (* number of terms of A120963 *)
nmax2 = Floor[terms/2] - 1;
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];
A341711[n_ /; 0 <= n <= nmax2] := A120963[[2 n + 2]]/2;
K[n_] := A341711[Floor[n/2]];
a[n_] := If[n == 0, 2, K[n - 1] + K[n] + K[n + 1]];
Table[a[n], {n, 0, nmax1}] (* Jean-François Alcover, Dec 01 2023 *)

Crossrefs

Cf. A341711.

Sequence in context: A073602 A057025 A055469 * A327552 A336342 A284354

Adjacent sequences: A361148 A361149 A361150 * A361152 A361153 A361154

Keyword

nonn

Author

N. J. A. Sloane, Mar 02 2023

Status

approved