A106840 Numbers m such that both m and m+1 have odd part of the form 4*k+1.

1, 4, 8, 9, 16, 17, 20, 25, 32, 33, 36, 40, 41, 49, 52, 57, 64, 65, 68, 72, 73, 80, 81, 84, 89, 97, 100, 104, 105, 113, 116, 121, 128, 129, 132, 136, 137, 144, 145, 148, 153, 160, 161, 164, 168, 169, 177, 180, 185, 193, 196, 200, 201, 208, 209, 212, 217, 225

Offset: 1

Author

Ralf Stephan, May 03 2005

Keywords

• nonn

Comments

From Amiram Eldar, Sep 14 2024: (Start)

Disjoint union of A017077 and {4*A091072(n)}.

The asymptotic density of this sequence is 1/4. (End)

Examples

			20/4 = 5 == 1 (mod 4) and also 21 == 1 (mod 4), therefore 20 is in the sequence.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A017077, A091072, A106841, A106837.

Contains A106841 and A106841+1.

Programs

Mathematica

f[n_] := Mod[n / 2^IntegerExponent[n, 2] - 1, 4]; SequencePosition[Array[f, 250], {0, 0}][[;;,1]] (* Amiram Eldar, Sep 14 2024 *)