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Search: id:A145338
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| A145338 |
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a(n) = the smallest prime p where |d(p-1) - d(p+1)| = n. (d(m) = the number of divisors of m.) |
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+0
2
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| 7, 2, 11, 197, 23, 37, 47, 401, 59, 1601, 181, 16901, 167, 3137, 179, 577, 419, 1297, 1051, 12101, 359, 739601, 1009, 4357, 1511, 50177, 719, 171610001, 839, 67601, 10657, 9096257, 1439, 240101, 3697, 145540097, 3023, 15877, 2879, 3587237, 2521
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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a(2n-1) = k^2 + 1, for all positive integers n, where k is some integer; k is even for n>=2.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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a(2)=11 because abs(d(10)-d(12))=2 while abs(d(p-1)-d(p+1))<2 for p=2,3,5 and 7. [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 11 2008]
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MAPLE
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with(numtheory); a:=proc(n) local j: for j while abs(tau(ithprime(j)-1)-tau(ithprime(j)+1)) <> n do end do: ithprime(j) end proc: seq(a(n), n=0..26); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 11 2008]
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CROSSREFS
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A145337
Sequence in context: A021141 A147677 A090243 this_sequence A104586 A040048 A070429
Adjacent sequences: A145335 A145336 A145337 this_sequence A145339 A145340 A145341
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Oct 08 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric Deutsch (deutsch(AT)duke.poly.edu), Oct 10 2008
Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Oct 12 2008 from a(27) onwards
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