A065516 - OEIS

%I #27 Dec 26 2020 02:10:36

%S 2,3,1,4,1,6,1,3,1,7,1,1,3,1,7,3,2,4,2,1,4,3,4,5,3,5,3,1,1,4,2,1,1,11,

%T 5,4,3,1,2,1,1,6,4,1,7,1,1,2,1,9,3,1,2,5,3,8,1,5,2,2,7,7,1,1,2,1,3,4,

%U 1,1,2,1,1,2,5,9,2,10,2,4,1,5,3,3,2,7,4,9,2,2,4,3,1,2,1,1,2,4,5,5,2,2,3,1,2

%N Differences between products of 2 primes.

%C See A215231 and A085809 for record values and where they occur: A215231(n) = a(A085809(n)). - _Reinhard Zumkeller_, Mar 23 2014

%H T. D. Noe, <a href="/A065516/b065516.txt">Table of n, a(n) for n=1..10000</a>

%F a(n) = A001358(n+1) - A001358(n).

%e a(6) = A001358(7) - A001358(6) = 21 - 15 = 6.

%t Differences[Select[Range[329], PrimeOmega[#] == 2 &]] (* _Arkadiusz Wesolowski_, Nov 24 2011 *)

%o (PARI) {spg(m)=local(a,b); a=0; b=4; for(n=5,m,if(bigomega(n) == 2,a=n; print1(a-b","); b=a; ))}

%o (Haskell)

%o a065516 n = a065516_list !! (n-1)

%o a065516_list = zipWith (-) (tail a001358_list) a001358_list

%o -- _Reinhard Zumkeller_, Mar 23 2014

%Y A166237 is the version for distinct primes.

%Y Cf. A001358, A239656.

%K easy,nonn

%O 1,1

%A _Lior Manor_, Nov 27 2001

%E More terms from _Jason Earls_, Jul 24 2003