A210616 - OEIS

%I #11 Dec 06 2021 16:55:01

%S 4,6,9,1,41,51,12,22,52,62,33,43,53,83,93,64,94,15,55,75,85,26,56,96,

%T 47,77,28,58,68,78,19,39,49,59,601,111,511,811,911,121,221,321,921,

%U 331,431,141,241,341,541,641,551,851,951,161,661,961,771,871,381

%N Digit reversal of n-th semiprime.

%C The fixed points where a(n) = n are A046328.

%H Alois P. Heinz, <a href="/A210616/b210616.txt">Table of n, a(n) for n = 1..2000</a>

%F a(n) = R(A001358(n)) = A004086(A001358(n)).

%t t = Select[Range[200], PrimeOmega[#] == 2 &]; FromDigits[Reverse[IntegerDigits[#]]] & /@ t (* _T. D. Noe_, Mar 26 2012 *)

%t IntegerReverse/@Select[Range[500],PrimeOmega[#]==2&] (* _Harvey P. Dale_, Dec 06 2021 *)

%Y Cf. A001358, A004086, A046328.

%K nonn,base,easy

%O 1,1

%A _Jonathan Vos Post_, Mar 23 2012