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 A200832 Primes of the form (2^k + k)*2^k + 1. 7
 7, 89, 4481, 268664833, 4398090551297, 18014402133360641, 5070602400913032447777310769153, 5316911983139663632271651803156709377, 102844034832575377634685573910878950656009052628932024900517889 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The generalization of this sequence is possible with the primes of the form (b^n +- k)*b^n +- 1. The corresponding indices k are 1, 3, 6, 14, 21, 27, 51, 61, 103, 123, 126, 414, 499, 1509, 2389, ... (see A200823). For k = 103, a(9) has 63 digits; for k = 123, a(10) has 75 digits; for k = 126, a(11) has 76 digits; for k = 414, a(12) has 250 digits; for k = 499, a(13) has 301 digits; for k = 1509, a(14) has 909 digits; for k = 2389, a(15) has 1439 digits. LINKS Henri Lifchitz, New forms of primes EXAMPLE 89 is in the sequence because, for k = 3, (2^3 + 3)*2^3 + 1 = 89 is prime. MATHEMATICA a={}; Do[p=(2^n + n)*2^n+1; If[PrimeQ[p], AppendTo[a, p]], {n, 10^3}]; Print[a]; CROSSREFS Cf. A200816, A200817, A200818, A200819, A200821, A200822, A200823. Sequence in context: A099719 A142995 A350937 * A103064 A244849 A355591 Adjacent sequences: A200829 A200830 A200831 * A200833 A200834 A200835 KEYWORD nonn AUTHOR Michel Lagneau, Nov 23 2011 STATUS approved

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Last modified March 25 01:20 EDT 2023. Contains 361511 sequences. (Running on oeis4.)