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A163981
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a(n) is the smallest prime of the form prime(n+1)*k - prime(n), k >= 1, where prime(n) is the n-th prime.
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2
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7, 2, 2, 37, 2, 89, 2, 73, 151, 2, 43, 127, 2, 239, 59, 419, 2, 73, 359, 2, 401, 419, 1163, 881, 307, 2, 967, 2, 569, 3697, 397, 691, 2, 457, 2, 163, 821, 839, 179, 1259, 2, 2111, 2, 1777, 2, 223, 3803, 3863, 2, 3499, 1201, 2, 2269, 263, 269, 1889, 2, 283, 1409, 2, 2647
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OFFSET
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1,1
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COMMENTS
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LINKS
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MAPLE
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a := proc (n) local k: for k while isprime(ithprime(n+1)*k-ithprime(n)) = false do end do: ithprime(n+1)*k-ithprime(n) end proc: seq(a(n), n = 1 .. 65); # Emeric Deutsch, Aug 10 2009
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MATHEMATICA
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a[n_] := Module[{p, q, r}, For[p = Prime[n]; q = Prime[n + 1]; k = 1, True, k++, If[PrimeQ[r = q k - p], Return[r]]]];
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PROG
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(Python)
from sympy import isprime, nextprime, prime
def a(n):
pn = prime(n); pn1 = nextprime(pn); k = 1
while not isprime(pn1*k - pn): k += 1
return pn1*k - pn
(PARI) a(n) = my(k=1); while (!isprime(p=prime(n+1)*k - prime(n)), k++); p; \\ Michel Marcus, Jul 02 2021
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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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STATUS
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approved
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