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.

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

Author

Jason Earls, Jun 02 2004

Keywords

• easy
• nonn
• base

Examples

			201 is a term because both 201 and 1000 - 201 = 799 are semiprimes.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A089186.

Programs

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 *)