cp's OEIS Frontend

A374104 a(n) = A075860(A075860(n) + 2) + 2.

%I A374104 #17 Jul 23 2024 21:40:19
%S A374104 4,4,7,4,9,9,5,4,7,5,15,9,4,7,4,4,21,9,9,5,5,4,7,9,9,4,7,7,33,5,5,4,7,
%T A374104 9,9,9,4,5,4,5,45,9,4,4,4,9,9,9,5,5,5,4,4,9,4,7,4,5,63,5,9,7,5,4,9,4,
%U A374104 4,9,4,7,75,9,4,4,4,5,9,9,5,5,7,4,15,9,4,4,4,4,9,5,5,9
%N A374104 a(n) = A075860(A075860(n) + 2) + 2.
%C A374104 (p,p+2) is a twin prime pair if and only if a(p)=p+4.
%C A374104 For all positive integers n, there exists a positive integer m such that a(n)<a(m).
%p A374104 g:= proc(n) option remember;
%p A374104     if isprime(n) then n
%p A374104    else procname(convert(numtheory:-factorset(n), `+`))
%p A374104     fi
%p A374104  end proc:
%p A374104  g(1):= 0:
%p A374104 seq(2+g(2+g(i)),i=1..140);
%o A374104 (PARI) fp(n, pn) = if (n == pn, n, fp(vecsum(factor(n)[, 1]), n));
%o A374104 f(n) = if (n==1, 0, fp(n, 0)); \\ A075860
%o A374104 a(n) = f(f(n)+2)+2; \\ _Michel Marcus_, Jun 28 2024
%Y A374104 Cf. A075860, A008472.
%K A374104 nonn
%O A374104 1,1
%A A374104 _Rafik Khalfi_, Jun 28 2024