A140546 Primes p such that neither p - 6 nor p + 6 is prime.

2, 3, 71, 127, 139, 149, 181, 211, 241, 281, 293, 349, 397, 401, 409, 419, 421, 431, 479, 487, 491, 499, 521, 523, 617, 631, 643, 661, 673, 691, 701, 709, 719, 743, 761, 769, 773, 787, 797, 809, 811, 839, 907, 911, 919, 929, 937, 967, 1009, 1021, 1031, 1049

Offset: 1

Author

Juri-Stepan Gerasimov, Jun 30 2008

Keywords

• nonn
• easy

Links

• N. J. A. Sloane, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A136207 (complement)

Programs

Maple

isA140546 := proc(n)
    if isprime(n) then
        if isprime(n+6) or isprime(n-6) then
            false;
        else
            true;
        end if;
    else
        false ;
    end if;
end proc:
A140546 := proc(n)
    option remember;
    local a;
    if n = 1 then
        2 ;
    else
        a := nextprime(procname(n-1)) ;
        while true do
            if isA140546(a) then
                return a;
            else
                a := nextprime(a) ;
            end if;
        end do:
    end if;
end proc:
seq(A140546(n),n=1..80) ; # R. J. Mathar, Jun 10 2024

Mathematica

Select[Prime[Range[176]],!PrimeQ[#+6]&&(!PrimeQ[#-6]||#<5)&] (* James C. McMahon, Jul 12 2025 *)

Extensions

Corrected and extended by Charles R Greathouse IV, Mar 25 2010