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A078493
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One-prime decades.
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0
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90, 110, 120, 140, 180, 210, 240, 290, 300, 360, 390, 410, 420, 450, 470, 480, 550, 580, 630, 660, 680, 690, 710, 720, 740, 770, 780, 790, 800, 810, 830, 860, 870, 900, 920, 930, 950, 960, 980, 1000, 1020, 1040, 1050, 1080, 1110, 1160, 1170, 1190, 1200, 1240
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OFFSET
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0,1
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COMMENTS
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The year 2003 is the only prime year in the 2000 decade.
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LINKS
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MATHEMATICA
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Select[10*Range[200], PrimePi[#+10]-PrimePi[#]==1&] (* Harvey P. Dale, Apr 13 2020 *)
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PROG
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(PARI) decade1(n1, n2) = { forstep(x=n1, n2, 10, if(isprime(x+1) && !isprime(x+3) && !isprime(x+7) && !isprime(x+9), print1(x" "); ); if(isprime(x+3) && !isprime(x+1) && !isprime(x+7) && !isprime(x+9), print1(x" "); ); if(isprime(x+7) && !isprime(x+1) && !isprime(x+3) && !isprime(x+9), print1(x" "); ); if(isprime(x+9) && !isprime(x+1) && !isprime(x+3) && !isprime(x+7), print1(x" "); ); ); }
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CROSSREFS
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KEYWORD
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easy,nonn,base
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AUTHOR
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STATUS
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approved
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