A105575 -id:A105575 - cp's OEIS frontend

A123272 Number of primes between consecutive terms of A105575.

1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0

Offset: 1

Giovanni Teofilatto, Oct 10 2006

Cf. A105575.

a(n) = PrimePi(A105575(n+1)) - PrimePi(A105575(n)) - 1.

Edited and extended by Ray Chandler, Oct 17 2006

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

Original entry on oeis.org

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

Giovanni Teofilatto, May 05 2005

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

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

Cf. A105399, A105575.

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 *)

Extended by Ray Chandler, Oct 17 2006

cp's OEIS Frontend

A123272 Number of primes between consecutive terms of A105575.

Views

Author

Keywords

Crossrefs

Formula

Extensions

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

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Mathematica

Extensions