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 A181492 Primes of the form p=3*2^k+1 such that p-2 is also a prime. 7
 7, 13, 193, 786433 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sequence A181490 lists the exponents k, sequences A181491 and A181493 the corresponding lesser twin prime and their average. LINKS FORMULA A181492 = A181491 + 2 = A181493 + 1 = 3*2^A181490 + 1 = intersection of A004119 or A103204 or A181495 with A006512 or A001097. MATHEMATICA Select[3 2^Range[100]+1, And@@PrimeQ[{#, #-2}]&] (* Harvey P. Dale, Jun 19 2013 *) PROG (PARI) for( k=1, 999, ispseudoprime(3<

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Last modified January 21 05:39 EST 2020. Contains 331104 sequences. (Running on oeis4.)