A108137 - OEIS

A108137

Primes p such that p + 6^k is composite for all k >= 0.

3, 19, 29, 59, 79, 89, 109, 139, 149, 179, 199, 229, 239, 269, 349, 359, 379, 389, 409, 419, 439, 449, 479, 499, 509, 569, 599, 619, 659, 709, 719, 739, 769, 809, 829, 839, 859, 919, 929

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OFFSET

1,1

COMMENTS

The PARI code given suggests that these values are merely conjectures. - N. J. A. Sloane, Jun 30 2005

Except for the first term, these primes are of the form 10n+9. It follows that 10n+9 + (5+1)^k = 5H not prime for some H for all n and k.

Superset of A030433. [From R. J. Mathar, Aug 24 2008]

LINKS

Table of n, a(n) for n=1..39.

PROG

(PARI) pplus2ton(n, m, b) = \defiant primes base b { local(k, s, p, y, flag); s=0; forprime(p=2, n, flag=1; for(k=0, m, y=p+b^k; if(ispseudoprime(y), \ print1(k, ", "); s++; flag=0; break) ); if(flag, print1(p", ")); \search for defiant primes. ); print(); print(s); }

CROSSREFS

Sequence in context: A062619 A339864 A180451 * A250027 A339545 A102978

Adjacent sequences: A108134 A108135 A108136 * A108138 A108139 A108140

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Jun 27 2005

STATUS

approved