%I A081770
%S A081770 4,12,20,28,44,52,60,68,76,84,92,116,124,132,140,148,156,164,172,188,
%T A081770 204,212,220,228,236,244,260,268,276,284,292,308,316,332,340,348,356,
%U A081770 364,372,380,388,404,412,420,428,436,444,452,460,476,492,508,516,524
%N A081770 Numbers twice their square-free kernel (A007947).
%C A081770 a(n) = 2*A039956(n)= 4*A056911(n).
%e A081770 84=2*2*3*7=2*(2*3*7)=2*sfk(84), therefore 84 is a term.
%Y A081770 Cf. A013929, A005117.
%Y A081770 Sequence in context: A141065 A031065 A017113 this_sequence A062876 A085039 
               A038429
%Y A081770 Adjacent sequences: A081767 A081768 A081769 this_sequence A081771 A081772 
               A081773
%K A081770 nonn
%O A081770 1,1
%A A081770 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 10 2003