This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A210616 #11 Dec 06 2021 16:55:01 %S A210616 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 A210616 47,77,28,58,68,78,19,39,49,59,601,111,511,811,911,121,221,321,921, %U A210616 331,431,141,241,341,541,641,551,851,951,161,661,961,771,871,381 %N A210616 Digit reversal of n-th semiprime. %C A210616 The fixed points where a(n) = n are A046328. %H A210616 Alois P. Heinz, <a href="/A210616/b210616.txt">Table of n, a(n) for n = 1..2000</a> %F A210616 a(n) = R(A001358(n)) = A004086(A001358(n)). %t A210616 t = Select[Range[200], PrimeOmega[#] == 2 &]; FromDigits[Reverse[IntegerDigits[#]]] & /@ t (* _T. D. Noe_, Mar 26 2012 *) %t A210616 IntegerReverse/@Select[Range[500],PrimeOmega[#]==2&] (* _Harvey P. Dale_, Dec 06 2021 *) %Y A210616 Cf. A001358, A004086, A046328. %K A210616 nonn,base,easy %O A210616 1,1 %A A210616 _Jonathan Vos Post_, Mar 23 2012