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 A196303 Numbers n such that both n and (n-1)*2^n+1 are primes. 0
 2, 3, 7, 1471, 1483, 61627, 88731 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes p such that (p-1)*2^p+1 is also prime. LINKS EXAMPLE a(1)=2 because 2 and (2-1)*2^2+1=5 are both prime. a(2)=3 because 3 and (3-1)*2^3+1=17 are both prime. a(3)=7 because 7 and (7-1)*2^7+1=769 are both prime. MATHEMATICA Select[Prime[Range], PrimeQ[(#-1)2^#+1]&] (* Harvey P. Dale, Jan 19 2012 *) PROG (PARI) forprime(n=1, 1e4, if(ispseudoprime((n-1)<

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Last modified June 3 05:29 EDT 2020. Contains 334798 sequences. (Running on oeis4.)