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 A248816 #23 May 29 2024 03:17:47 %S A248816 152,284,4316,18632,25484,2657259,8394752,12186976,17702756, %T A248816 1172473731,2147581952,13716855652,63831498112 %N A248816 Numbers that are equal to the arithmetic derivative of the sum of their aliquot parts. %C A248816 Solutions of the equations n = (sigma(n)-n)'. %C A248816 a(12) > 5*10^9. - _Michel Marcus_, Nov 01 2014 %C A248816 There could be a relation with terms in A125246 and A228450, since some terms of these sequences are here also. - _Michel Marcus_, Oct 30 2014 %C A248816 a(14) > 10^11. - _Giovanni Resta_, May 29 2016 %e A248816 Sum of the aliquot parts of 284 is sigma(284) - 284 = 220 and the arithmetic derivative of 220 is 284.~ %p A248816 with(numtheory): P:= proc(q) local a,n,p; for n from 1 to q do %p A248816 a:=(sigma(n)-n)*add(op(2,p)/op(1,p),p=ifactors(sigma(n)-n)[2]); %p A248816 if n=a then print(n); fi; od; end: P(10^9); %o A248816 (PARI) ad(n) = sum(i=1, #f=factor(n)~, n/f[1, i]*f[2, i]); %o A248816 isok(n) = ad(sigma(n) - n) == n; \\ _Michel Marcus_, Oct 28 2014 %Y A248816 Cf. A000203, A003415, A230164. %K A248816 nonn,more %O A248816 1,1 %A A248816 _Paolo P. Lava_, Oct 15 2014 %E A248816 a(6)-a(11) from _Michel Marcus_, Oct 28 2014 %E A248816 a(12)-a(13) from _Giovanni Resta_, May 29 2016