A374104 - OEIS

A374104

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

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, 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, 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

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OFFSET

1,1

COMMENTS

(p,p+2) is a twin prime pair if and only if a(p)=p+4.

For all positive integers n, there exists a positive integer m such that a(n)<a(m).

LINKS

Table of n, a(n) for n=1..92.

MAPLE

g:= proc(n) option remember;

if isprime(n) then n

else procname(convert(numtheory:-factorset(n), `+`))

end proc:

g(1):= 0:

seq(2+g(2+g(i)), i=1..140);

PROG

(PARI) fp(n, pn) = if (n == pn, n, fp(vecsum(factor(n)[, 1]), n));

f(n) = if (n==1, 0, fp(n, 0)); \\ A075860

a(n) = f(f(n)+2)+2; \\ Michel Marcus, Jun 28 2024

CROSSREFS

Cf. A075860, A008472.

Sequence in context: A204156 A163106 A331619 * A258972 A146564 A048785

Adjacent sequences: A374101 A374102 A374103 * A374105 A374106 A374107

KEYWORD

nonn

AUTHOR

Rafik Khalfi, Jun 28 2024

STATUS

approved