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A070847
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Smallest prime == 1 mod (3n).
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7
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7, 7, 19, 13, 31, 19, 43, 73, 109, 31, 67, 37, 79, 43, 181, 97, 103, 109, 229, 61, 127, 67, 139, 73, 151, 79, 163, 337, 349, 181, 373, 97, 199, 103, 211, 109, 223, 229, 937, 241, 739, 127, 1033, 397, 271, 139, 283, 433, 883, 151, 307, 157, 3181, 163, 331, 337
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OFFSET
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1,1
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LINKS
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MAPLE
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f:= proc(n) local k, d;
if n::even then d:= 3*n else d:= 6*n fi;
for k from 1 by d do if isprime(k) then return k fi od
end proc:
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MATHEMATICA
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a[n_] := Module[{k, d}, If[EvenQ[n], d = 3n, d = 6n]; For[k = 1, True, k += d, If[PrimeQ[k], Return[k]]]];
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PROG
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(PARI) for(n=1, 80, s=1; while((isprime(s)*s-1)%(3*n)>0, s++); print1(s, ", "))
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CROSSREFS
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Cf. A024892 (n such that a(n)=3*n+1).
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KEYWORD
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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