A078493 - OEIS

A078493

One-prime decades.

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

0,1

COMMENTS

The year 2003 is the only prime year in the 2000 decade.

LINKS

Table of n, a(n) for n=0..49.

MATHEMATICA

Select[10*Range[200], PrimePi[#+10]-PrimePi[#]==1&] (* Harvey P. Dale, Apr 13 2020 *)

PROG

(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" "); ); ); }

CROSSREFS

Sequence in context: A043224 A039401 A044004 * A176683 A135197 A025371

Adjacent sequences: A078490 A078491 A078492 * A078494 A078495 A078496

KEYWORD

easy,nonn,base

AUTHOR

Cino Hilliard, Jan 04 2003

STATUS

approved