A065516 Differences between products of 2 primes.

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, 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, 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

Offset: 1

Author

Lior Manor, Nov 27 2001

Keywords

• easy
• nonn

Comments

See A215231 and A085809 for record values and where they occur: A215231(n) = a(A085809(n)). - Reinhard Zumkeller, Mar 23 2014

Examples

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

Links

• T. D. Noe, Table of n, a(n) for n=1..10000

Crossrefs

A166237 is the version for distinct primes.

Cf. A001358, A239656.

Programs

Haskell

a065516 n = a065516_list !! (n-1)
a065516_list = zipWith (-) (tail a001358_list) a001358_list
-- Reinhard Zumkeller, Mar 23 2014

Mathematica

Differences[Select[Range[329], PrimeOmega[#] == 2 &]] (* Arkadiusz Wesolowski, Nov 24 2011 *)

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; ))}

Formula

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

Extensions

More terms from Jason Earls, Jul 24 2003