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A247793
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Least integer m > 0 such that pi(m*n) divides prime(m) + prime(n), where pi(x) denotes the number of primes not exceeding x.
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3
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2, 1, 75, 10, 18, 1, 75, 41, 58, 2, 94, 107, 14, 13, 2, 14, 14, 1, 84, 527, 124, 715, 13, 4, 1, 4, 276, 310, 2, 4, 11216, 3074, 3470, 14, 2, 15, 5, 947, 538839, 2, 8, 2, 1592, 4, 8, 16813, 2293, 1, 2755, 3007, 3272, 32203, 5357440, 6, 17, 17, 374252, 9, 17, 6905
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OFFSET
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1,1
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COMMENTS
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Conjecture: a(n) exists for any n > 0.
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LINKS
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EXAMPLE
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a(4) = 10 since pi(4*10) = 12 divides prime(4) + prime(10) = 7 + 29 = 36.
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MATHEMATICA
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Do[m=1; Label[aa]; If[m*n>1&&Mod[Prime[m]+Prime[n], PrimePi[m*n]]==0, Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa]; Label[bb]; Continue, {n, 1, 60}]
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PROG
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(Haskell)
a247793_list = 2 : f (zip [2..] $ tail a000040_list) where
f ((x, p) : xps) = m : f xps where
m = head [y | y <- [1..], (p + a000040 y) `mod` a000720 (x * y) == 0]
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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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