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A094298
Numbers m such that m and its 10's complement are both semiprimes, i.e., m and 10^k - m, where k is the number of digits of m, are semiprime.
1
4, 6, 14, 15, 26, 35, 38, 49, 51, 62, 65, 74, 85, 86, 91, 94, 111, 121, 122, 129, 134, 158, 159, 169, 183, 185, 187, 201, 206, 209, 215, 219, 221, 237, 247, 254, 287, 301, 302, 303, 305, 319, 321, 326, 329, 365, 371, 377, 386, 403, 411, 417, 427, 446, 447, 458
OFFSET
1,1
LINKS
EXAMPLE
201 is a term because both 201 and 1000 - 201 = 799 are semiprimes.
MAPLE
tc:= n -> 10^(1+ilog10(n))-n:
filter:= proc(n) numtheory:-bigomega(n)=2 and numtheory:-bigomega(tc(n))=2 end proc:
select(filter, [$1..1000]); # Robert Israel, Jul 02 2024
MATHEMATICA
Select[Range[500], PrimeOmega[#]==PrimeOmega[10^IntegerLength[#]-#]==2&] (* Harvey P. Dale, Jan 17 2013 *)
CROSSREFS
Sequence in context: A310616 A310617 A305842 * A338045 A089226 A102029
KEYWORD
easy,nonn,base
AUTHOR
Jason Earls, Jun 02 2004
STATUS
approved