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A091440 Smallest number m such that m#/phi(m#) >= n, where m# indicates the primorial (A002110) of m and phi is Euler's totient function. 2
1, 2, 3, 7, 13, 23, 43, 79, 149, 257, 461, 821, 1451, 2549, 4483, 7879, 13859, 24247, 42683, 75037, 131707, 230773, 405401, 710569, 1246379, 2185021, 3831913, 6720059, 11781551, 20657677, 36221753, 63503639, 111333529, 195199289 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Does the ratio of adjacent terms converge?

LINKS

Table of n, a(n) for n=1..34.

Eric Weisstein's World of Mathematics, Totient Function

Eric Weisstein's World of Mathematics, Primorial

EXAMPLE

7#/phi(7#) = (2*3*5*7)/(1*2*4*6) = 4.375 >= 4, 5#/phi(5#) = 3.75. Hence a(4) = 7.

MATHEMATICA

prod=1; i=0; Table[While[prod<n, i++; prod=prod/(1-1/Prime[i])]; Prime[i], {n, 1, 20}]

PROG

(PARI) al(lim) = local(mm, n, m); mm=3; n=2; m=1; forprime(x=3, lim, n*=x; m*= (x-1); if (n\m >= mm, print1(x", "); mm++)); /* This will generate all terms of this sequence from the 3rd onward, up to lim. The computation slows down for large values because of the size of the internal values. */ - Fred Schneider, Aug 13 2009, modified by Franklin T. Adams-Watters, Aug 29 2009

CROSSREFS

Cf. A091439, A000010, A002110, A038110, A060753, A164347.

Sequence in context: A144104 A088175 A271827 * A175211 A075058 A213968

Adjacent sequences:  A091437 A091438 A091439 * A091441 A091442 A091443

KEYWORD

nonn

AUTHOR

T. D. Noe, Jan 09 2004

EXTENSIONS

More terms from David W. Wilson, Sep 28 2005

STATUS

approved

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Last modified March 23 02:49 EDT 2017. Contains 283901 sequences.