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A178216
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a(n) = prime(A178215(n)) mod prime(n).
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1
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1, 1, 4, 1, 10, 12, 1, 1, 22, 27, 1, 32, 10, 33, 27, 24, 1, 24, 8, 48, 72, 55, 39, 69, 44, 22, 16, 105, 44, 56, 14, 76, 87, 129, 22, 138, 85, 50, 82, 130, 69, 93, 18, 60, 135, 170, 105, 110, 225, 44
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OFFSET
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1,3
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COMMENTS
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a(n) is the last residue modulo prime(n) in the minimal set of the first primes which contains all residues modulo prime(n).
Build the smallest set {prime(1), prime(2), ..., prime(k)} of the first k consecutive primes such that the set {prime(1) mod prime(n), prime(2) mod prime(n), ..., prime(k) mod prime(n)} contains all residues {0, 1, 2, ..., prime(n)-1}. Then a(n) = prime(k) mod prime(n). - R. J. Mathar, Oct 25 2010
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LINKS
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EXAMPLE
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If n=3, then prime(n)=5 and {2,3,5,7,11,13,17,19} is the minimal set of the first primes which contains all residues modulo 5. We have consecutive residues {2,3,0,2,1,3,2,4}. Therefore a(3)=4.
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MAPLE
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A178216 := proc(n) local p, k, modP, i ; p := ithprime(n) ; for k from 1 do modP := [seq( ithprime(j) mod p, j=1..k)] ; {seq(i, i=0..p-1)} minus convert(modP, set) ; if % = {} then return op(-1, modP) ; end if; end do: end proc: seq(A178216(n), n=1..50) ; # R. J. Mathar, Oct 25 2010
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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a(10) corrected, more terms appended by R. J. Mathar, Oct 25 2010
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STATUS
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approved
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