A070847 Smallest prime == 1 mod (3n).

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

Robert Israel, Table of n, a(n) for n = 1..10000

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. A070846, A070848, A070849, A070850, A070851, A070852, A070853.

Cf. A034694.

Cf. A024892 (n such that a(n)=3*n+1).

Cf. A002476.

Sequence in context: A358380 A139126 A070919 * A195863 A053416 A213031

Adjacent sequences: A070844 A070845 A070846 * A070848 A070849 A070850

Keyword

nonn,look

Author

Amarnath Murthy, May 15 2002

Extensions

More terms from Benoit Cloitre, May 18 2002

Status

approved