A209489 a(n) = A306912(n) - 2.
0, 1, 3, 6, 12, 19, 33, 50, 77, 111, 166, 229, 329, 448, 615, 824, 1120, 1467, 1956, 2538, 3313, 4258, 5512, 6993, 8944, 11278, 14258, 17838, 22402, 27788, 34629, 42747, 52832, 64844, 79706, 97232, 118868, 144392, 175474, 212168, 256750
Offset: 1
Keywords
Programs
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Mathematica
p[n_] := p[n] = IntegerPartitions[n]; l[n_] := Length[p[n]]; p[n_, j_] := p[n, j] = Part[p[n], j] g[n_, j_] := g[n, j] = Apply[GCD, p[n, j]] h[n_] := h[n] = Table[g[n, j], {j, 1, l[n]}] c[n_] := c[n] = Count[h[n], 1] Table[c[n], {n, 0, 45}] (* A000837 *) s[n_] := Sum[c[k], {k, 1, n}] Table[s[n] - 1, {n, 1, 45}]
Formula
a(n) = Sum_{k=2..n} A000837(k).
Extensions
New name and edits made by Clark Kimberling, Dec 18 2024
Comments