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Search: id:A077149
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| A077149 |
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a(1) =3. For n>1, a(n) = smallest k such that there are n numbers m not relatively prime to n in range n < m < k. |
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+0
2
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| 3, 7, 13, 13, 31, 16, 57, 25, 37, 27, 133, 31, 183, 39, 49, 49, 307, 46, 381, 55, 71, 63, 553, 61, 151, 75, 109, 78, 871, 71, 993, 97, 118, 99, 148, 91, 1407, 111, 142, 107, 1723, 101, 1893, 125, 142, 135, 2257, 121, 393, 135, 188, 149, 2863, 136, 256, 155
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(p) = p^2 + p +1, a(2^m) = 3*2^m +1,a(p^m) = p^m + p^(m+1) +1, if p is a prime.
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EXAMPLE
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a(5) = 31 as there are 5 non-coprime numbers to 5 between 5 and 31, i.e. 10,15,20,25 and 30.
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PROGRAM
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(PARI) print1("3, "):for(n=2, 100, s=0:for(k=n+1, 10^9, if(gcd(n, k)>1, s=s+1): if(s==n, s=k:break)):print1(s+1", "))
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CROSSREFS
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Cf. A077148.
Adjacent sequences: A077146 A077147 A077148 this_sequence A077150 A077151 A077152
Sequence in context: A128156 A108768 A118889 this_sequence A064829 A035496 A056530
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Oct 30 2002
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EXTENSIONS
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More terms from Ralf Stephan (ralf(AT)ark.in-berlin.de), Mar 25 2003
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