A057922 - OEIS

%I #12 May 08 2019 16:41:55

%S 1,2,5,7,11,13,14,17,19,21,23,26,29,31,33,34,37,38,39,41,43,44,47,49,

%T 53,55,57,59,61,65,67,69,71,73,75,77,79,83,85,86,87,89,93,94,95,97,98,

%U 101,103,104,107,109,113,116,118,119,122,125,127,129,131,133,134,135

%N d(n) divides d(n+1), where d(n) is number of positive divisors of n.

%H Ivan Neretin, <a href="/A057922/b057922.txt">Table of n, a(n) for n = 0..10000</a>

%e 11 is included because d(11) = 2 divides d(12) = 6.

%t Select[Range@150, Divisible @@ DivisorSigma[0, {# + 1, #}] &] (* _Ivan Neretin_, May 29 2015 *)

%t Position[Partition[DivisorSigma[0,Range[150]],2,1],_?(Divisible[#[[2]], #[[1]]]&),1,Heads->False]//Flatten (* _Harvey P. Dale_, May 08 2019 *)

%Y Cf. A057921, A005237.

%K nonn

%O 0,2

%A _Leroy Quet_, Nov 11 2000