cp's OEIS Frontend

A376844 Numbers k such that (k + k')' = k' + k'', where ' denotes the arithmetic derivative A003415.

%I A376844 #7 Oct 08 2024 07:19:24
%S A376844 1,2,16,98,108,275,598,729,2419,3503,5324,11304,12500,35937,50498,
%T A376844 51179,58339,76302,84375,107830,141775,209663,324480,588800,618434,
%U A376844 1090123,1532188,2190240,2615251,3175699,3294172,3974400,4159375,6795761,8403500,8831250,9765625,10342269,14784120,15714364,16056320
%N A376844 Numbers k such that (k + k')' = k' + k'', where ' denotes the arithmetic derivative A003415.
%e A376844 a(4) = 98 is a term because 98' = 77, 77' = 18 and (98  + 77)' = 175' = 95 = 77 + 18.
%p A376844 deriv:= proc(n) local t; add(n*t[2]/t[1], t = ifactors(n)[2]) end proc:
%p A376844 filter:= proc(n) local s; s:= deriv(n); deriv(n+s) = s + deriv(s) end proc:
%p A376844 select(filter, [$1..10^6]);
%Y A376844 Cf. A003415, A376830, A376831, A376843, A376848, A376849, A376851.
%K A376844 nonn
%O A376844 1,2
%A A376844 _Robert Israel_, Oct 06 2024