A263106 - OEIS

%I #15 Jul 23 2023 01:54:07

%S 4,6,9,15,22,26,33,39,49,51,55,58,62,77,85,93,94,111,122,129,134,141,

%T 145,155,158,159,161,177,178,183,185,187,202,206,214,226,254,262,298,

%U 303,309,314,321,339,341,355,358,362,371,381,391,393,394,403,407,413

%N Semiprimes such that the leftward cyclic permutation of its decimal digits is also semiprime.

%C First 18 terms are also in A085751.

%H Zak Seidov, <a href="/A263106/b263106.txt">Table of n, a(n) for n = 1..65049</a> (all terms up to 10^6)

%e 15 = 3 * 5, 51 = 3 * 17; 889 = 7 * 17, 898 = 2 * 449.

%t Select[Range[4, 1000], 2 == PrimeOmega[#] == PrimeOmega[FromDigits[RotateLeft[IntegerDigits[#]]]] &]

%o (PARI) shl(n)=if(n<10,return(n)); my(d=digits(n)); fromdigits(concat(d[2..#d], d[1]))

%o is(n)=bigomega(n)==2 && bigomega(shl(n))==2 \\ _Charles R Greathouse IV_, Oct 12 2015

%Y Cf. A001292, A001358, A085751.

%K nonn,base

%O 1,1

%A _Zak Seidov_, Oct 09 2015