A105792 Largest prime <= numbers congruent (2,4) mod 6 (duplicates removed).

2, 3, 7, 13, 19, 23, 31, 37, 43, 47, 53, 61, 67, 73, 79, 83, 89, 97, 103, 109, 113, 127, 131, 139, 151, 157, 163, 167, 173, 181, 193, 199, 211, 223, 229, 233, 241, 251, 257, 263, 271, 277, 283, 293, 307, 313, 317, 331, 337, 349, 353, 359, 367, 373, 379, 383, 389

Offset: 1

Author

Giovanni Teofilatto, May 05 2005

Keywords

• easy
• nonn

Comments

Except for the first terms, largest prime p is at least < two numbers congruent (2,4) mod 6.

Examples

			7 is in the sequence because 7 is the largest prime < 8 which is a number congruent (2,4) mod 6.
		

Crossrefs

Cf. A105399, A105575.

Programs

Mathematica

pp[n_] := Block[{k = n},While[ ! PrimeQ[k], k-- ];k];Union[pp /@ Select[Range[400], MemberQ[{2, 4}, Mod[ #, 6]] &]] (* Ray Chandler, Oct 17 2006 *)
Union[Abs[NextPrime[#,-1]&/@Select[Range[400],MemberQ[{2,4}, Mod[ #,6]]&]]] (* Harvey P. Dale, May 17 2012 *)

Extensions

Extended by Ray Chandler, Oct 17 2006