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 A369651 #8 Jan 31 2024 16:55:59 %S A369651 0,0,1,1,32,1,1,37712,381596,9835475,36880858,5221912091,149759057759, %T A369651 186024798,456607833524310,655374897748042,32188411533060, %U A369651 3002590335363139484,1,1,1489192548103758778136571,905624730150525686386253700,1,110832638787270947169636975150,331748330219014906068858,349669183443106226663011852002384 %N A369651 The second arithmetic derivative of primorial numbers. %C A369651 See comments in A024451. %H A369651 Antti Karttunen, <a href="/A369651/b369651.txt">Table of n, a(n) for n = 0..49</a> %F A369651 a(n) = A003415(A024451(n)) = A068346(A002110(n)). %o A369651 (PARI) %o A369651 A002110(n) = prod(i=1,n,prime(i)); %o A369651 A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1])); %o A369651 A369651(n) = A003415(A003415(A002110(n))); %Y A369651 Cf. A002110, A003415, A024451, A068346, A109628 (positions of 1's). %Y A369651 Cf. also A368702. %K A369651 nonn %O A369651 0,5 %A A369651 _Antti Karttunen_, Jan 31 2024