A307308 Self-composition of the Euler totient function (A000010).

1, 2, 6, 15, 42, 106, 280, 702, 1778, 4398, 10910, 26678, 65172, 157656, 380524, 912846, 2185906, 5216588, 12433166, 29564544, 70189672, 166245574, 392909240, 926290066, 2178881218, 5114469170, 11985221654, 28049398284, 65588182636, 153277006212, 358073997608

Offset

1,2

Links

Vaclav Kotesovec, Table of n, a(n) for n = 1..500

Eric Weisstein's World of Mathematics, Totient Function

Formula

G.f.: g(g(x)), where g(x) = Sum_{k>=1} mu(k)*x^k/(1 - x^k)^2 is the g.f. of A000010.

Mathematica

g[x_] := g[x] = Sum[MoebiusMu[k] x^k/(1 - x^k)^2, {k, 1, 31}]; a[n_] := a[n] = SeriesCoefficient[g[g[x]], {x, 0, n}]; Table[a[n], {n, 31}]

Crossrefs

Cf. A000010, A008683, A010554, A065093, A307309.

Sequence in context: A236110 A362566 A280782 * A065178 A178936 A221744

Adjacent sequences: A307305 A307306 A307307 * A307309 A307310 A307311

Keyword

nonn

Author

Ilya Gutkovskiy, Apr 02 2019

Status

approved