



1, 2, 3, 4, 2, 4, 2, 3, 6, 1, 2, 4, 3, 4, 5, 7, 6, 5, 6, 7, 6, 7, 4, 2, 4, 3, 8, 5, 6, 8, 6, 2, 8, 3, 7, 4, 8, 6, 10, 10, 7, 10, 9, 10, 12, 10, 2, 4, 6, 11, 7, 4, 10, 6, 5, 7, 11, 2, 3, 9, 5, 8, 6, 8, 12, 7, 11, 10, 12, 1, 3, 11, 4, 10, 8, 7, 10, 4, 15, 12, 6
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..81.


EXAMPLE

A286843(1)  A001065(A286843(1)) = 10  8 = 2 = 2^1, thus a(1) = 1.


MATHEMATICA

t=Select[Table[2n, {n, 1, 7*10^7}], DivisorSigma[1, 2#DivisorSigma[1, #]]+1 == 2(2#DivisorSigma[1, #])>2 &]; u=Table[2t[[k]]DivisorSigma[1, t[[k]], {k, 81}]; Log[2, u] (* or *)
Select[Log2[2 #  DivisorSigma[1, #]] & /@ (2 Range@33500), IntegerQ[#] && # > 0 &] (* Giovanni Resta, Aug 08 2017 *)


CROSSREFS

Cf. A000079, A001065, A286843.
Sequence in context: A330954 A107468 A023632 * A338272 A107572 A043264
Adjacent sequences: A286841 A286842 A286843 * A286845 A286846 A286847


KEYWORD

nonn


AUTHOR

XU Pingya, Aug 07 2017


STATUS

approved



