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A152735 Count of links in n-th maximal chain of primes. 9
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 16 14:39 EDT 2021. Contains 343949 sequences. (Running on oeis4.)