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A070847
Smallest prime == 1 mod (3n).
7
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
OFFSET
1,1
LINKS
MAPLE
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:
map(f, [$1..100]); # Robert Israel, Sep 19 2019
MATHEMATICA
a[n_] := Module[{k, d}, If[EvenQ[n], d = 3n, d = 6n]; For[k = 1, True, k += d, If[PrimeQ[k], Return[k]]]];
Array[a, 100] (* Jean-François Alcover, Jun 11 2020, after Maple *)
PROG
(PARI) for(n=1, 80, s=1; while((isprime(s)*s-1)%(3*n)>0, s++); print1(s, ", "))
CROSSREFS
Cf. A034694.
Cf. A024892 (n such that a(n)=3*n+1).
Cf. A002476.
Sequence in context: A358380 A139126 A070919 * A195863 A053416 A213031
KEYWORD
nonn,look
AUTHOR
Amarnath Murthy, May 15 2002
EXTENSIONS
More terms from Benoit Cloitre, May 18 2002
STATUS
approved