

A060735


Where n / (phi(n) + 1) increases.


17



1, 2, 4, 6, 12, 18, 24, 30, 60, 90, 120, 150, 180, 210, 420, 630, 840, 1050, 1260, 1470, 1680, 1890, 2100, 2310, 4620, 6930, 9240, 11550, 13860, 16170, 18480, 20790, 23100, 25410, 27720, 30030, 60060, 90090, 120120, 150150, 180180, 210210
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OFFSET

1,2


COMMENTS

Except for the initial 1, this sequence is a primorial (A002110) followed by its multiples until the next primorial, then the multiples of that primorial and so on.  Wilfredo Lopez (chakotay147138274(AT)yahoo.com), Dec 28 2006
a(1)=1, a(2)=2. For n >=3, a(n) = the smallest integer that both is > a(n1) and is divisible by every prime that LCM(a(1),a(2),a(3),...a(n)) is divisible by. [From Leroy Quet, Feb 23 2010]


LINKS

Enrique Pérez Herrero, Table of n, a(n) for n = 1..5000
Michel Planat, Riemann hypothesis from the Dedekind psi function, arXiv:1010.3239v2.


FORMULA

a(1) = 1, a(n) = a(n1) + rad(a(n1)) with rad=A007947, squarefree kernel.  Reinhard Zumkeller, Apr 10 2006
a(A101301(n)+1)=A002110(n).  Enrique Pérez Herrero, Jun 10 2012


MAPLE

seq(seq(k*mul(ithprime(i), i=1..n1), k=1..ithprime(n)1), n=1..10); (from Vladeta Jovovic, Apr 08 2004)


MATHEMATICA

a = 0; Do[ b = n/(EulerPhi[ n ] + 1); If[ b > a, a = b; Print[ n ] ], {n, 1, 10^6} ]


CROSSREFS

Cf. A000010, A055719, A002110.
Sequence in context: A072121 A175305 A171923 * A181416 A225566 A051683
Adjacent sequences: A060732 A060733 A060734 * A060736 A060737 A060738


KEYWORD

nonn


AUTHOR

Robert G. Wilson v, Apr 23 2001


EXTENSIONS

Definition corrected by Franklin T. AdamsWatters, Apr 16 2009


STATUS

approved



