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A067836
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Let a(1)=2, f(n)=a(1)*a(2)*...*a(n-1) for n>=1 and a(n)=nextprime(f(n)+1)-f(n) for n>=2, where nextprime(x) is the smallest prime > x.
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10
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2, 3, 5, 7, 13, 11, 17, 19, 23, 37, 73, 29, 31, 43, 79, 53, 83, 67, 41, 47, 179, 149, 181, 103, 71, 59, 197, 167, 109, 137, 107, 251, 101, 157, 199, 283, 211, 277, 173, 127, 269, 61, 89, 271, 151, 191, 227, 311, 409, 577, 331, 281, 313, 307, 223, 491, 439, 233, 367
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OFFSET
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1,1
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COMMENTS
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The terms are easily seen to be distinct. It is conjectured that every element is prime. Do all primes occur in the sequence?
All elements are prime and distinct through n=1000. - Robert Price, Mar 09 2013
All elements are prime and distinct through n=3724. - Dana Jacobsen, Feb 15 2015
With a(0) = 1, a(n) is the next smallest number not in the sequence such that a(n) + Product_{i=1..n-1} a(i) is prime. - Derek Orr, Jun 16 2015
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LINKS
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MATHEMATICA
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<<NumberTheory`PrimeQ` (* Load ProvablePrimeQ function, needed below. *)
f[1]=1; f[n_] := f[n]=f[n-1]a[n-1]; a[n_] := a[n]=Module[{i}, For[i=2, True, i++, If[ProvablePrimeQ[f[n]+i], Return[i]]]]
Join[{a = 2}, f = 1; Table[f = f*a; a = NextPrime[f + 1] - f; a, {n, 2, 59}]] (* Jayanta Basu, Aug 10 2013 *)
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PROG
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(MuPAD) f := 1:for n from 1 to 50 do a := nextprime(f+2)-f:f := f*a:print(a) end_for
(PARI) v=[2]; n=2; while(n<500, s=n+prod(i=1, #v, v[i]); if(isprime(s)&&!vecsearch(vecsort(v), n), v=concat(v, n); n=1); n++); v \\ Derek Orr, Jun 16 2015
(Python)
from sympy import nextprime
def A067836_gen(): # generator of terms
a, f = 2, 1
yield 2
while True:
yield (a:=nextprime((f:=f*a)+1)-f)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Frank Buss (fb(AT)frank-buss.de), Feb 09 2002
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EXTENSIONS
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STATUS
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approved
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