|
%I #28 Aug 20 2024 03:10:11
%S 1,1,2,2,2,3,2,3,2,3,2,3,3,3,2,2,3,1,3,2,2,2,2,3,3,3,4,2,3,3,3,2,3,2,
%T 3,3,2,4,3,2,3,3,2,4,3,3,3,3,3,4,2,3,3,2,3,3,3,2,3,3,2,3,3,3,4,2,2,3,
%U 3,3,2,3,3,2,3,2,3,4,3,3,4,3,2,2,3,2,3,3,4,4,3,4,3,4,3,3,3,3,3,2,3,3,2,4,3
%N Number of distinct prime factors of sum of 2 successive primes.
%H G. C. Greubel, <a href="/A071215/b071215.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = omega(prime(n) + prime(n + 1)) = A001221(A001043(n)), where omega is the number of distinct prime factors function.
%e Prime(6) = 13 and prime(7) = 17. 13 + 17 = 30 = 2 * 3 * 5, which has three distinct prime factors, hence a(6) = 3.
%t Table[PrimeNu[Prime[n] + Prime[n + 1]], {n, 105}] (* _Jean-François Alcover_, Oct 21 2013 *)
%o (PARI) A071215(n)=omega(prime(n)+prime(n+1)) \\ _M. F. Hasler_, Jul 23 2007
%Y Cf. A001043, A001221, A071216.
%K easy,nonn,changed
%O 1,3
%A _Labos Elemer_, May 17 2002
|
