2*2*3-1=11 2*2*3+1=13, 11 and 13 twin primes so a(2)=3
2*2*3*5-1=59 2*2*3*5+1=61, 59 and 61 twin primes so a(3)=5
MAPLE
isA001359 := proc(n) RETURN(isprime(n) and isprime(n+2)); end: primo := 2 : print(primo); for n from 2 to 20000 do p := ithprime(n); primo := primo*p; if isA001359(2*primo-1) then print(p); fi; od : - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 09 2006
