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%I #15 Feb 22 2024 02:22:33
%S 5,11,19,29,41,0,71,89,109,131,0,181,0,239,271,0,0,379,419,461,0,0,
%T 599,0,701,0,811,0,929,991,0,0,0,1259,0,0,1481,1559,0,1721,0,0,1979,
%U 2069,2161,0,2351,0,2549,0
%N a(n) = n^2 + 3*n + 1 if prime or 0 if composite.
%e 1^2+3*1+1 = 5 prime so a(1) = 5.
%e 2^2+3*2+1 = 11 prime so a(2) = 11.
%e 6^2+3*6+1 = 55 = 5*11 composite so a(6) = 0.
%t Table[t=n^2+3n+1;If[PrimeQ[t],t,0],{n,50}] (* _James C. McMahon_, Feb 21 2024 *)
%Y Cf. A028387.
%K nonn,less
%O 1,1
%A _Pierre CAMI_, Jun 06 2005
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