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URL: https://oeis.org/A286844

⇱ A286844 - OEIS

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A286844
a(n) = log_2(A286843(n) - A001065(A286843(n))).
0
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
OFFSET
1,2
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
KEYWORD
nonn
AUTHOR
XU Pingya, Aug 07 2017
STATUS
approved