A054012 Nonzero values of n read modulo (number of proper divisors of n).

2, 1, 1, 2, 2, 3, 1, 3, 1, 2, 3, 2, 2, 1, 2, 4, 2, 5, 4, 1, 3, 1, 2, 5, 1, 1, 5, 2, 3, 4, 2, 3, 3, 6, 2, 1, 2, 1, 8, 1, 1, 7, 1, 2, 4, 2, 1, 2, 1, 2, 8, 3, 4, 4, 4, 6, 1, 9, 5, 4, 2, 1, 1, 2, 1, 2, 1, 2, 4, 2, 5, 2, 4, 1, 2, 2, 3, 5, 8, 1, 2, 4, 1, 2, 2, 3, 7, 5, 3, 2, 2, 2, 6, 2, 4, 4, 1, 3, 1, 2, 1, 2, 6, 5, 1

Offset: 1

Author

Asher Auel, Jan 17 2000

Keywords

• nonn

Crossrefs

Cf. A000005, A032741, A054009, A054011.

Programs

Maple

with(numtheory):
[seq(`if`(i mod (tau(i)-1) <> 0,i mod (tau(i)-1),print( )), i=2..220)];

Mathematica

Cases[Table[Mod[n,DivisorSigma[0,n]-1],{n,2,200}],Except[0]] (* Harvey P. Dale, Nov 12 2011 *)

Formula

a(n) = A054011(A054009(n)).