A152735 Count of links in n-th maximal chain of primes.

2, 3, 1, 1, 2, 4, 3, 1, 1, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 1, 1, 2, 1, 2, 4, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 6, 1, 4, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 2, 2, 2, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 2, 1

Offset

1,1

Comments

One less than count of members of n-th maximal chain of primes. For definitions see A152658.

Links

Klaus Brockhaus, Table of n, a(n) for n=1..1000

Example

The consecutive primes 5, 7, 11 form the first maximal chain of primes (see example in A152658); it has three members, two links. Therefore a(1) = 2.

Prog

(PARI) {n=1; while(n<560, c=0; while(isprime(n*prime(n)+(n+1)*prime(n+1)), c++; n++); if(c>0, print1(c, ", ")); n++)}

Crossrefs

Cf. A152658 (beginnings of maximal chains of primes), A152657 (secluded primes), A119487 (primes of the form i*(i-th prime) + (i+1)*((i+1)-th prime), linking primes).

Sequence in context: A193280 A114732 A123338 * A249128 A299481 A304738

Adjacent sequences: A152732 A152733 A152734 * A152736 A152737 A152738

Keyword

nonn

Author

Klaus Brockhaus, Dec 16 2008

Status

approved