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A229480 Primes formed by inserting a semiprime between the semiprime's ordered factors. 4
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 (list; graph; refs; listen; history; text; internal format)
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: A054802 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

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Last modified September 23 02:41 EDT 2021. Contains 347609 sequences. (Running on oeis4.)