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

1,1

Links

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

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

Cf. A001358, A089186.

Sequence in context: A310616 A310617 A305842 * A338045 A089226 A102029

Adjacent sequences: A094295 A094296 A094297 * A094299 A094300 A094301

Keyword

easy,nonn,base

Author

Jason Earls, Jun 02 2004

Status

approved