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A302387
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a(n) is least number k >= 3 such that (k^(2^n) + (k-2)^(2^n))/2 is prime.
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0
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3, 3, 3, 5, 3, 3, 3, 179, 169, 935, 663, 8723, 1481, 2035, 10199, 18203
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OFFSET
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0,1
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LINKS
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Table of n, a(n) for n=0..15.
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EXAMPLE
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a(10)=663 corresponds to the prime (663^1024 + 661^1024)/2.
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MATHEMATICA
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lst = {}; For[n=0, n<=14, n++, k=3; While[! PrimeQ[(k^(2^n) + (k-2)^(2^n))/2], k++]; AppendTo[lst, k]]; lst (* Robert Price, Apr 29 2018 *)
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PROG
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(PARI) for(n=0, 20, forstep(k=3, +oo, 2, if(ispseudoprime((k^(2^n)+(k-2)^(2^n))/2), print1(k, ", "); break())))
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CROSSREFS
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Cf. A253633, A291944, A301738.
Sequence in context: A084742 A242033 A301738 * A049613 A002373 A236569
Adjacent sequences: A302384 A302385 A302386 * A302388 A302389 A302390
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KEYWORD
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nonn,hard,more
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AUTHOR
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Jeppe Stig Nielsen, Apr 06 2018
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EXTENSIONS
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a(15) from Robert Price, May 28 2018
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STATUS
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approved
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