

A181414


Products of exactly two Pillai primes.


0



529, 667, 841, 1357, 1403, 1541, 1633, 1711, 1769, 1817, 1909, 1943, 2059, 2291, 2407, 2507, 3161, 3481, 3599, 3721, 3953, 4087, 4189, 4331, 4489, 4661, 4757, 4819, 4897, 5041, 5063, 5293, 5561, 5609, 5893, 6241, 6431, 6557, 6649, 6889
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OFFSET

1,1


COMMENTS

It would not be right to call these "Pillai semiprimes" as that would better describe semiprimes k such that there exists an integer m such that m!+1 is 0 mod k and k is not 1 mod m.
There are no pairs (n, n+1) in this sequence since all terms are odd. The first few n such that n and n+2 are in the sequence are 11771, 14099, 19337, 32729, 32741, 34829, 37391, 38249, 39467, 40319, 41747, ...  Charles R Greathouse IV, Jan 28 2011


LINKS

Table of n, a(n) for n=1..40.


FORMULA

{A063980(i) * A063980(j)}.


EXAMPLE

a(2) = 23*29.


CROSSREFS

Cf. A001358, A063980.
Sequence in context: A205160 A205309 A045788 * A020289 A274932 A082409
Adjacent sequences: A181411 A181412 A181413 * A181415 A181416 A181417


KEYWORD

nonn,easy


AUTHOR

Jonathan Vos Post, Jan 28 2011


STATUS

approved



