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A062251
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Take minimal prime q such that n(q+1)-1 is prime (A060324), that is, the smallest prime q so that n = (p+1)/(q+1) with p prime; sequence gives values of p.
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8
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2, 5, 11, 11, 19, 17, 41, 23, 53, 29, 43, 47, 103, 41, 59, 47, 67, 53, 113, 59, 83, 131, 137, 71, 149, 103, 107, 83, 173, 89, 433, 127, 131, 101, 139, 107, 443, 113, 233, 239, 163, 167, 257, 131, 179, 137, 281, 191, 293, 149, 1019, 311, 211, 431, 439, 167, 227
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refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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A conjecture of Schinzel, if true, would imply that such a p always exists.
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LINKS
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FORMULA
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EXAMPLE
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1 = (2+1)/(2+1), 2 = (5+1)/(2+1), 3 = (11+1)/(3+1), 4 = (11+1)/(2+1), ...
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MAPLE
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a:= proc(n) local q;
q:= 2;
while not isprime(n*(q+1)-1) do
q:= nextprime(q);
od; n*(q+1)-1
end:
seq(a(n), n=1..300);
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MATHEMATICA
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a[n_] := (q = 2; While[ ! PrimeQ[n*(q+1)-1], q = NextPrime[q]]; n*(q+1)-1); Table[a[n], {n, 1, 57}] (* Jean-François Alcover, Feb 17 2012, after Maple *)
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PROG
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(Haskell)
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CROSSREFS
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KEYWORD
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nonn,nice,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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