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A188815
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Least prime p such that prime(n) divides p + nextprime(p).
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3
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3, 5, 2, 19, 97, 23, 31, 73, 67, 347, 89, 109, 199, 83, 281, 631, 233, 607, 131, 421, 727, 1103, 743, 353, 577, 907, 307, 641, 433, 1237, 251, 389, 271, 829, 593, 449, 1879, 487, 331, 3109, 1609, 3257, 1907, 383, 2357, 1987, 3163, 443, 2719, 683, 1861, 6211, 719, 2251, 769, 3943, 5647, 2437, 4153, 3371, 563, 877, 3677, 929, 937
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(5) = 97 because 97 + 101 = 198, and prime(5) = 11 is the largest prime divisor
of 198.
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MAPLE
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with(numtheory):for n from 1 to 100 do: nn:=ithprime(n):id:=0:for k from 1
to 2000 while(id=0) do:x:=ithprime(k+1)+ithprime(k): if irem(x, nn)=0 then id:=1:printf(`%d,
`, ithprime(k)):else fi:od:od:
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MATHEMATICA
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Table[p = 2; q = 3; While[Mod[p + q, Prime[n]] > 0, p = q; q = NextPrime[q]]; p, {n, 65}]
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PROG
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(PARI) a(n) = {my(pn=prime(n)); my(p=2); forprime(q=3, , if ((p+q) % pn, p = q, break); ); p; } \\ Michel Marcus, Jul 05 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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