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A259979
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Numbers that are both 1 + square of a prime and twice a prime.
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1
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10, 26, 122, 362, 842, 3482, 3722, 5042, 6242, 10202, 17162, 19322, 32762, 39602, 73442, 121802, 143642, 167282, 201602, 212522, 271442, 323762, 326042, 398162, 410882, 436922, 546122, 564002, 674042, 776162, 863042, 982082, 1062962, 1079522, 1104602, 1142762, 1190282, 1274642, 1324802, 1371242
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Select[Range[2*10^6], PrimeQ[Sqrt[#-1]]&&PrimeQ[#/2]&] (* Ivan N. Ianakiev, Jul 13 2015 *)
Select[Prime@ Range[10^4], PrimeQ[(#^2 + 1)/2] &]^2 + 1 (* faster, Giovanni Resta, Jul 13 2015 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane, Jul 12 2015, following a suggestion of R. P. Boas, May 19, 1974
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EXTENSIONS
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STATUS
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approved
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