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A088423 a(n) is the number of primes in arithmetic progression starting with 11 and with d = 2n. 10

%I

%S 2,1,4,2,1,2,1,1,3,2,1,1,2,1,5,2,1,3,1,1,2,1,1,3,2,1,1,2,1,6,2,1,1,2,

%T 1,2,1,1,3,1,1,1,2,1,4,2,1,2,2,1,2,1,1,1,1,1,1,2,1,3,1,1,4,2,1,1,1,1,

%U 2,2,1,1,2,1,1,2,1,2,1,1,2,1,1,3,2,1,1,1,1,2,2,1,4,2,1,1,1,1,1,2

%N a(n) is the number of primes in arithmetic progression starting with 11 and with d = 2n.

%C Arithmetic progression is stopped when next term is not prime. E.g., for n=3, a=4, that is 11,17,23,29 are prime, while next term, 35, is not prime.

%H Michael De Vlieger, <a href="/A088423/b088423.txt">Table of n, a(n) for n = 1..10000</a>

%t bb={}; Do[s=1; Do[If[PrimeQ[11+k*d], s=s+1, bb={bb, s}; Break[]], {k, 10}], {d, 2, 200, 2}]; Flatten[bb]

%o (PARI) a(n) = my(p=11, x=p+2*n, i=1); while(1, if(ispseudoprime(x), i++; x=x+2*n, return(i))) \\ _Felix Fröhlich_, May 28 2021

%Y Cf. A088420, A088421, A088422, A088424, A088425, A088426, A088427, A088428, A088429.

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Sep 29 2003

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Last modified June 23 13:59 EDT 2021. Contains 345402 sequences. (Running on oeis4.)