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Search: id:A091440
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| A091440 |
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Smallest number m such that m#/phi(m#) >= n, where m# indicates the primorial (A002110) of m and phi is Euler's totient function. |
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3
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| 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; listen)
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OFFSET
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1,2
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COMMENT
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Does the ratio of adjacent terms converge?
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LINKS
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Eric Weisstein's World of Mathematics, Totient Function
Eric Weisstein's World of Mathematics, Primorial
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EXAMPLE
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7#/phi(7#) = (2*3*5*7)/(1*2*4*6) = 4.375 >= 4, 5#/phi(5#) = 3.75. Hence a(4) = 7.
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MATHEMATICA
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prod=1; i=0; Table[While[prod<n, i++; prod=prod/(1-1/Prime[i])]; Prime[i], {n, 1, 20}]
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PROGRAM
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(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 (frederick.william.schneider(AT)gmail.com), Aug 13 2009, modified by Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Aug 29 2009
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CROSSREFS
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Cf. A091439, A000010, A002110, A038110, A060753, A164347.
Sequence in context: A133370 A144104 A088175 this_sequence A075058 A128695 A024504
Adjacent sequences: A091437 A091438 A091439 this_sequence A091441 A091442 A091443
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Jan 09 2004
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EXTENSIONS
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More terms from David W Wilson (davidwwilson(AT)comcast.net), Sep 28 2005
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