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Search: id:A139795
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| A139795 |
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Least m such that k>=m implies phi(k)>=n (where phi is the Euler totient function, sequence A000010). |
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+0
2
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| 1, 3, 7, 7, 13, 13, 19, 19, 31, 31, 31, 31, 43, 43, 43, 43, 61, 61, 61, 61, 67, 67, 67, 67, 91, 91, 91, 91, 91, 91, 91, 91, 121, 121, 121, 121, 127, 127, 127, 127, 151, 151, 151, 151, 151, 151, 151, 151, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211, 211
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Define b(n)=A006511(m)+1 where m is the unique integer such that A002202(m)<n<=A002202(m+1) (with the convention A002202(0)=A006511(0)=0). Then a(1)=b(1) and a(n+1)=max(a(n),b(n+1)).
The sequence a(n) without the repetitions is 1+A036913(n).
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LINKS
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Max Alekseyev, Table of n, a(n) for n = 1..10000
Max Alekseyev, PARI scripts for various problems (see invphi.gp there).
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EXAMPLE
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a(5)=13 because if k>=13, then phi(k)>=5, but phi(12)=4.
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PROGRAM
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(PARI) {m=0; for(n=1, 100, print1(m+1, ", "); trap(, 0, m=max(m, vecmax(invphi(n)))))}
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CROSSREFS
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Different from A137315 (see Comments in that entry).
Sequence in context: A024612 A073881 A137315 this_sequence A118259 A060845 A060215
Adjacent sequences: A139792 A139793 A139794 this_sequence A139796 A139797 A139798
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KEYWORD
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nonn
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AUTHOR
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Benoit Jubin (benoit_jubin(AT)yahoo.fr), May 21 2008
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