cp's OEIS Frontend

A369969 Numbers that are not multiples of 5, but their arithmetic derivative is.

%I A369969 #8 Dec 05 2024 20:14:40
%S A369969 1,6,21,26,32,36,46,51,76,86,88,91,99,106,111,112,116,126,141,146,156,
%T A369969 161,166,192,201,206,209,216,221,226,236,242,243,248,266,272,276,279,
%U A369969 291,301,306,308,316,319,321,326,328,346,356,369,371,381,386,391,392,406,411,429,436,441,446,456,466,471,481,488,501
%N A369969 Numbers that are not multiples of 5, but their arithmetic derivative is.
%H A369969 Robert Israel, <a href="/A369969/b369969.txt">Table of n, a(n) for n = 1..10000</a>
%p A369969 filter:= proc(n) local F, np, t;
%p A369969   if n mod 5 = 0 then return false fi;
%p A369969   F:= ifactors(n)[2];
%p A369969   np:= add(n*t[2]/t[1],t=F);
%p A369969   np mod 5 = 0
%p A369969 end proc:
%p A369969 select(filter, [$1..1000]); # _Robert Israel_, Dec 05 2024
%o A369969 (PARI) \\ See A369968.
%Y A369969 Intersection of A047201 and A327865.
%Y A369969 Includes A050997 \ {3125} as a subsequence.
%Y A369969 Cf. A003415, A369968 (characteristic function).
%Y A369969 Cf. also A046337, A369659, A360110 for cases k=2, 3, 4 of "Nonmultiples of k whose arithmetic derivative is a multiple of k".
%K A369969 nonn
%O A369969 1,2
%A A369969 _Antti Karttunen_, Feb 10 2024