A286844 a(n) = log_2(A286843(n) - A001065(A286843(n))).
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
Keywords
Examples
A286843(1) - A001065(A286843(1)) = 10 - 8 = 2 = 2^1, thus a(1) = 1.
Programs
-
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 *)