A161500 Primes dividing some member of A073833.

2, 5, 29, 41, 89, 101, 109, 269, 421, 509, 521, 709, 929, 941, 1549, 1861, 2281, 2521, 2749, 2801, 2909, 3121, 3169, 3469, 5821, 5881, 7109, 8069, 8969, 9041, 9181, 10061, 10601, 11549, 15121, 16061, 16889, 16981, 21929, 30089, 30169, 32561, 41149

Offset

1,1

Comments

Primes that divide A073833(n) will divide A073834(m) for any m > n, and this is all the prime divisors of A073834(m).

Iterating f(x) = x + 1/x modulo p will eventually either produce a zero (in which case p is in this sequence), or it will loop to an earlier term (in which case it is not). Since f(-x) = -f(x), encountering the negation of an earlier term means that the iteration is looping.

Note that A073833(6) = 969581 = 521 * 1861 is the first composite member of that sequence.

Links

Table of n, a(n) for n=1..43.

Prog

(PARI) ina(p)=local(m, k, v); m=Mod(1, p); v=vector(p\2); while(m!=0, k=lift(m); if(2*k>p, k=p-k); if(v[k], return(0)); v[k]=1; m+=1/m); 1

Crossrefs

Cf. A073833, A073834, A000057.

Sequence in context: A370513 A134449 A103579 * A061351 A126107 A193901

Adjacent sequences: A161497 A161498 A161499 * A161501 A161502 A161503

Keyword

nonn

Author

Franklin T. Adams-Watters, Jun 11 2009

Status

approved