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 A281686 #10 Jan 27 2017 17:21:29 %S A281686 4,8,9,14,21,25,26,27,32,33,36,38,46,48,49,50,54,57,62,69,74,80,85,88, %T A281686 93,94,99,100,106,121,125,128,129,133,134,145,156,166,169,176,177,178, %U A281686 205,207,213,216,217,218,226,230,237,240,242,243,248,249,252,253 %N A281686 Numbers k such that A001222(k) = A001222(A003415(k)). %C A281686 Numbers k such that the number of prime divisors (counted with multiplicity) of k is equal to the number of prime divisors (counted with multiplicity) of the arithmetic derivative of k. %H A281686 Colin Barker, <a href="/A281686/b281686.txt">Table of n, a(n) for n = 1..1000</a> %o A281686 (PARI) arde(n) = sum(i=1, #f=factor(n)~, n/f[1, i]*f[2, i]) %o A281686 select(k->bigomega(k)==bigomega(arde(k)), vector(400, k, k+1)) %Y A281686 Cf. A001222, A003415, A209870, A281685. %K A281686 nonn %O A281686 1,1 %A A281686 _Colin Barker_, Jan 27 2017