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 A316712 Numbers k such that 421*2^k+1 is prime. 0
 4, 8, 12, 16, 24, 36, 72, 196, 576, 928, 3336, 5172, 5996, 6196, 13204, 28484, 36984, 43740, 58744, 62244, 112876, 127852, 143208, 170612, 174372, 221372, 350356, 832528, 1070460, 1729092, 2539336 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Ray Ballinger, Proth Search Page Ray Ballinger and Wilfrid Keller, List of primes k.2^n + 1 for 300 < k < 600 Wilfrid Keller, List of primes k.2^n - 1 for k < 300 Eric Weisstein's World of Mathematics, Proth Prime MAPLE select(k->isprime(421*2^k+1), [\$1..1000]); # Muniru A Asiru, Jan 05 2019 MATHEMATICA Select[Range[1000], PrimeQ[421*2^# + 1] &] CROSSREFS Sequence in context: A291834 A291928 A045783 * A261650 A178731 A334386 Adjacent sequences:  A316709 A316710 A316711 * A316713 A316714 A316715 KEYWORD nonn,more,hard AUTHOR Robert Price, Jan 04 2019 EXTENSIONS a(31) from Jeppe Stig Nielsen, Jan 04 2020 STATUS approved

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Last modified June 22 07:09 EDT 2021. Contains 345374 sequences. (Running on oeis4.)