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A296422
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Primes that can be represented in the form b^n+1 or b^n-1 where b >= 2 and n >= 2.
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1
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3, 5, 7, 17, 31, 37, 101, 127, 197, 257, 401, 577, 677, 1297, 1601, 2917, 3137, 4357, 5477, 7057, 8101, 8191, 8837, 12101, 13457, 14401, 15377, 15877, 16901, 17957, 21317, 22501, 24337, 25601, 28901, 30977, 32401, 33857, 41617, 42437, 44101, 50177, 52901
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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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N:= 10^5: # to get terms <= N
R:= 3:
for b from 2 while b^2+1 <= N do
p:= 2:
do
p:= nextprime(p);
if b^p-1 > N then break fi;
if isprime(b^p-1) then R:= R, b^p-1 fi;
od:
p:= 1:
do
p:= 2*p;
if b^p+1 > N then break fi;
if isprime(b^p+1) then R:= R, b^p+1 fi;
od;
od:
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MATHEMATICA
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Select[Prime@ Range[2, 10^4], AnyTrue[# + {-1, 1}, Or[# == 1, GCD @@ FactorInteger[#][[All, -1]] > 1] &] &] (* Michael De Vlieger, Dec 13 2017 *)
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PROG
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(PARI) lista(nn) = {forprime(p=2, nn, if ((p==2) || ispower(p+1) || ispower(p-1), print1(p, ", ")); ); } \\ Michel Marcus, Dec 13 2017
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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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