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A102811
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Least k such that, for j from 1 to n, 2*P(k+n-j) + 3 are consecutive primes with P(i)= i-th prime.
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1
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OFFSET
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1,2
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LINKS
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EXAMPLE
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For n = 1, 2*P(1) + 3 = 2*2 + 3 = 7 is prime, so a(1)=1 as P(1)=2.
For n = 2, 2*P(3) + 3 = 2*5 + 3 = 13 is prime, 2*P(4) + 3 = 2*7 + 3 = 17 is a prime consecutive to 13, so a(2)=3 as P(3)=5.
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PROG
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(PARI) a(n) = {my(m=1, p=vector(n, i, prime(i)), q); while(ispseudoprime(q=(2*p[1]+3)) + sum(k=2, n, (q=nextprime(q+1))==2*p[k]+3) < n, m++; p=concat(p[2..n], nextprime(p[n]+1))); m; } \\ Jinyuan Wang, Mar 20 2020
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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STATUS
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approved
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