A229480 Primes formed by inserting a semiprime between the semiprime's ordered factors.

263, 3217, 22613, 23417, 23819, 24623, 27437, 28643, 33311, 35117, 36923, 38729, 55511, 77711, 211859, 213467, 214673, 311137, 312943, 321371, 324983, 511523, 514529, 535571, 716123, 762389, 1118717, 1120919, 1125323, 1145141, 1151747, 1180373, 1322117, 1337729, 1732319

Offset

1,1

References

Chris K. Caldwell and G. L. Honaker, Jr., Prime Curios!, CreateSpace, 2009, Page 82.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

a(1)=263 because the semiprime 6 inserted between its ordered prime factors (2 and 3) is prime.

Prog

(PARI) list(lim)=my(v=List(), t); forprime(q=2, sqrtint(lim\10), forprime(p=2, min(sqrtint(lim\q), q), t=eval(Str(p, p*q, q)); if(t>lim, next(2)); if(isprime(t), listput(v, t)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Oct 01 2013

Crossrefs

Cf. A001358.

Sequence in context: A369877 A239685 A108823 * A266036 A157828 A065570

Adjacent sequences: A229477 A229478 A229479 * A229481 A229482 A229483

Keyword

nonn,base

Author

G. L. Honaker, Jr., Oct 01 2013

Extensions

a(4)-a(8), a(10)-a(35) from Charles R Greathouse IV, Oct 01 2013

Status

approved