A066519 Gaps between successive numbers with an anti-divisor class sum of zero.
1, 1, 3, 3, 6, 2, 4, 7, 2, 6, 7, 3, 1, 4, 3, 8, 7, 2, 1, 3, 5, 10, 2, 1, 3, 3, 2, 1, 5, 1, 1, 1, 4, 4, 2, 2, 2, 9, 2, 6, 9, 1, 1, 4, 4, 1, 3, 6, 1, 3, 22, 1, 9, 1, 1, 2, 2, 4, 7, 3, 5, 4, 1, 2, 20, 1, 2, 6, 1, 4, 4, 9, 5, 1, 4, 5, 2, 7, 8, 2, 2, 9, 2, 2, 1, 5, 3, 1, 4, 1, 12, 16, 13, 5, 1, 9, 2, 1, 3, 3
Offset: 1
Keywords
Examples
f(1)=f(2)=f(3)=0, f(4)=1, f(5)=-1, f(6)=0, so the first 3 gaps are 1, 1, 3.
Links
- Jon Perry, Class sums
Crossrefs
Cf. A066518.
Programs
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Mathematica
a[ n_ ] := Sum[ Which[ Mod[ n, d ]==(d-1)/2, -1, Mod[ n, d ]==(d+1)/2, 1, True, 0 ], {d, 2, n-1} ]; z=Select[ Range[ 1, 500 ], a[ # ]==0& ]; Drop[ z, 1 ]-Drop[ z, -1 ]
Extensions
Edited by Dean Hickerson, Jan 17 2002
Comments