

A167168


Sequence of prime gaps which characterize Rowland sequences of primegenerating recurrences.


11



3, 7, 17, 19, 31, 43, 53, 67, 71, 79, 97, 103, 109, 113, 127, 137, 151, 163, 173, 181, 191, 197, 199, 211, 229, 239, 241, 251, 257, 269, 271, 283, 293, 317, 331, 337, 349, 367, 373
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OFFSET

1,1


COMMENTS

Consider the Rowland sequences with recurrence N(n)= N(n1)+gcd(n,N(n1)).
For some of these, like the prototypical A106108, the first differences N(n)N(n1) are always 1 or primes.
If for some position p (a prime) N(p1)=2*p, then the arXiv preprint shows that N is indeed in that class of primegenerating sequences.
Since then N(p)=N(p1)+p, the prime p characterizes at the same time the gap (first difference) and location in the sequence.
In the same sequence at some larger value of p, we may again have N(p1)=2*p. In these cases, we put all these p's satisfying that equation into a generator class.
For each of the generator classes, the OEIS sequence shows the smallest member (prime) in that class. So this is a trace of how many essentially different sequences with this N(p1)=2*p property exist.


LINKS

Table of n, a(n) for n=1..39.
E. S. Rowland, A natural primegenerating recurrence, Journal of Integer Sequences, Vol. 11 (2008), Article 08.2.8
V. Shevelev, A new generator of primes based on the Rowland idea, arXiv:0910.4676 [math.NT], 2009.


EXAMPLE

We put a(1)=3 since the Nsequence 4, 6, 9, 10, 15, 18, 19, 20.. = A084662 (essentially the same as A106108) has a first difference of p=3 at position p1=2, N(2)=2*3.
It has a first difference of p=5 at p1=4, a first difference of p=11 at p=10, so we put {3,5,11,23,..} into that class. This leaves p=7=a(2) as the lowest prime to be covered by the next class. This is first realized by N = 8, 10, 11, 12, 13, 14, 21, 22, 23, 24, 25, 26, 39.. = A084663. Here N(12)=2*13, so p=13 is in the same class as p=7, namely {7,13,29,59,131,..}. This leaves p=17=a(3) to be the smallest member in a new class, namely {17,41,83,167,..}.


CROSSREFS

Cf. A106108, A167053, A116533, A163963, A084662, A084663, A134162.
Sequence in context: A087749 A140863 A076194 * A064699 A113304 A194945
Adjacent sequences: A167165 A167166 A167167 * A167169 A167170 A167171


KEYWORD

nonn


AUTHOR

Vladimir Shevelev, Oct 29 2009


EXTENSIONS

Edited, a(1) set to 3, 37 replaced by 31, and extended beyond 53 by R. J. Mathar, Dec 17 2009


STATUS

approved



