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 A122567 Twin primes modulo 4. 0

%I #2 Mar 31 2012 14:39:58

%S 3,1,3,3,1,1,3,1,3,1,3,3,1,3,1,1,3,3,1,1,3,1,3,3,1,3,1,1,3,3,1,3,1,1,

%T 3,1,3,3,1,3,1,3,1,3,1,1,3,1,3,1,3,3,1,1,3,1,3,3,1,1,3,1,3,3,1,1,3,1,

%U 3,3,1,3,1,1,3,1,3,3,1,3,1,1,3,1,3,1,3,1,3,3,1,3,1,3,1,1,3,3,1,3,1,3,1,3,1

%N Twin primes modulo 4.

%e The twin primes are 3,5,7,11,13,17,19,... and mod 4 is 3,1,3,3,1,1,3...

%p a[1]:=3:i:=2:for k from 5 to 3000 do if isprime(k) and isprime(k+2) then a[i]:=k mod 4:a[i+1]:=k+2 mod 4: i:=i+2 fi od: seq(a[n],n=1..i-1);

%Y Cf. A001097.

%K nonn

%O 1,1

%A _Miklos Kristof_, Sep 21 2006

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Last modified September 30 07:44 EDT 2023. Contains 365781 sequences. (Running on oeis4.)