First index k where A368558(k) = 2*n, or 0 if no such index exists.

Terms

a(0) =1a(1) =3a(2) =10a(3) =9a(4) =28a(5) =30a(6) =140a(7) =27a(8) =82a(9) =84a(10) =280a(11) =90a(12) =1148a(13) =420a(14) =5986a(15) =81a(16) =244a(17) =246a(18) =410a(19) =252a(20) =1342a(21) =840a(22) =2044a(23) =270a(24) =10004a(25) =656a(26) =97966a(27) =757a(28) =3028a(29) =7570