A087901 Twin primes associated with A087900.

5, 7, 29, 31, 179, 181, 1619, 1621, 21059, 21061, 463319, 463321, 11119679, 11119681, 567103679, 567103681, 52173538559, 52173538561, 6260824627199, 6260824627201, 1101905134387199, 1101905134387201, 284291524671897599, 284291524671897601, 77895877760099942399, 77895877760099942401

Offset: 1

Author

Lekraj Beedassy, Oct 14 2003

Keywords

• nonn
• tabf

Links

• Robert Israel, Table of n, a(n) for n = 1..418

Crossrefs

Cf. A087900.

Programs

Maple

R:= NULL; s:= 2: count:= 0:
for r from 3 while count < 30 do
    if isprime(s*r+1) and isprime(s*r-1) then
      count:= count+2; s:= s*r; R:= R,s-1,s+1;
    fi;
od:
R; # Robert Israel, Jun 11 2025

Formula

From Robert Israel, Jun 11 2025: (Start)

a(2*n-1) = (Product_{i=1..n+1} A087900(i)) - 1.

a(2*n) = (Product_{i=1..n+1} A087900(i)) + 1. (End)