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Search: id:A090873
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| A090873 |
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a(n) is the smallest number m such that n^2^k + m^2^k is prime for k=0,1,2,3 and 4. |
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+0
4
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| 1, 1, 218368, 9324385, 6628674, 601, 365082, 532253, 449140, 4193407, 175746, 2857547, 2752708, 6315245, 80612, 3354745, 10892, 953, 6577504, 157437, 2247676, 11357637, 7650, 272935, 318784, 8034141, 1158380, 22315, 610550, 340357
(list; graph; listen)
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OFFSET
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1,3
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FORMULA
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a[n_] := (For[m=1, !(PrimeQ[m+n]&&PrimeQ[m^2+n^2]&&PrimeQ[m^4+n^4]&& PrimeQ[m^8+n^8]&&PrimeQ[m^16+n^16]), m++ ];m)
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EXAMPLE
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a(2)=1 because 2^2^k + 1 is prime for k= 0,1,2,3 and 4.
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MATHEMATICA
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a[n_] := (For[m=1, !(PrimeQ[m+n]&&PrimeQ[m^2+n^2]&&PrimeQ[m^4+n^4]&& PrimeQ[m^8+n^8]&&PrimeQ[m^16+n^16]), m++ ]; m); Do[Print[a[n]], {n, 50}]
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CROSSREFS
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Cf. A090872, A019434, A000215.
Sequence in context: A078520 A019291 A157377 this_sequence A072189 A046396 A083640
Adjacent sequences: A090870 A090871 A090872 this_sequence A090874 A090875 A090876
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KEYWORD
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nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Feb 06 2004
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