OFFSET

1,1

COMMENTS

a(n) is surely larger than the n-th, but seems even larger than the (n+1)-th primorial number.

a(n) is neither necessarily squarefree nor it has a specified number of distinct prime-factors.

EXAMPLE

a(3) = 664, 663 = 3*13*17 and 665 = 5*11*19 both have three prime divisors.

MATHEMATICA

lf[x_] := Length[FactorInteger[x]] am[x_] := Abs[MoebiusMu[x]] q[x_] := Apply[Times, Table[Prime[j], {j, 1, x}]] Table[flag=1; Print["#"]; Do[s1=am[n-1]; s2=am[n+1]; If[Equal[s1, 1]&&Equal[s2, 1]&&Equal[lf[n-1], j] &&Equal[lf[n+1], j]&&Equal[flag, 1], Print[{n, j}]; flag=0], {n, q[j], q[j]+...}], {j, 1, 4}]

CROSSREFS

KEYWORD

nonn,hard,more

AUTHOR

Amarnath Murthy, Sep 22 2003

EXTENSIONS

Edited by Labos Elemer, Sep 26 2003

84946016 from Ray Chandler, Oct 09 2003

a(7) and a(8) from Donovan Johnson, Apr 22 2008

a(9)-a(11) from Donovan Johnson, Feb 18 2009

STATUS

approved