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A088420
Number of primes in arithmetic progression starting with 3 and with d = 2n.
10
3, 3, 1, 3, 3, 1, 3, 2, 1, 3, 1, 1, 2, 3, 1, 1, 3, 1, 3, 3, 1, 2, 1, 1, 3, 1, 1, 2, 2, 1, 1, 3, 1, 3, 2, 1, 1, 2, 1, 3, 1, 1, 2, 1, 1, 1, 3, 1, 3, 2, 1, 3, 2, 1, 3, 1, 1, 1, 1, 1, 1, 3, 1, 2, 1, 1, 3, 2, 1, 1, 1, 1, 2, 2, 1, 1, 3, 1, 1, 2, 1, 3, 1, 1, 2, 1, 1, 2, 3, 1, 1, 1, 1, 3, 3, 1, 2, 2, 1, 1
OFFSET
1,1
COMMENTS
The arithmetic progression is stopped when the next term is not prime. E.g., for n=5, a=3, the numbers 3, 13, and 23 are prime, while the next term, 33, is not prime.
a(n) <= 3 because 3+3*d is divisible by 3. - Klaus Brockhaus, May 14 2009
PROG
(Magma) npap3:=function(d) c:=1; p:=3+d; while IsPrime(p) do c+:=1; p+:=d; end while; return c; end function; [ npap3(2*n): n in [1..105] ]; // Klaus Brockhaus, May 14 2009
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Sep 29 2003
STATUS
approved