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A003510 An equivalence relation on permutations.
(Formerly M1510)
2
1, 1, 2, 5, 17, 67, 352, 1969, 13295, 97619, 848354, 7647499, 82862683, 897904165, 11226063188, 146116260203, 2089038231953, 30230018309161, 508450431515290, 8318618236423861, 154636109939564681, 2896102013935844771, 59056861862689101272 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

R. P. Stanley, Problem 5932, Amer. Math. Monthly, 82 (1975), 86-87.

R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.18.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

E.g.f.: exp ( Sum_{i=1..inf} x^i / i*phi(i) ), phi = Euler phi function (A000010).

MAPLE

with(numtheory); exp(add(x^n/(n*phi(n)), n=1..31));

MATHEMATICA

max = 22; f[x_] := Exp[ Sum[ x^k/(k*EulerPhi[k]), {k, 1, max}]]; CoefficientList[ Series[ f[x], {x, 0, max}], x]*Range[0, max]! (* Jean-Fran├žois Alcover, Oct 12 2011 *)

CROSSREFS

Sequence in context: A104082 A166474 A054769 * A051625 A056098 A239201

Adjacent sequences:  A003507 A003508 A003509 * A003511 A003512 A003513

KEYWORD

nonn,easy,nice

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified November 16 00:11 EST 2018. Contains 317252 sequences. (Running on oeis4.)