A279106 a(n) = number of legs in each part of the symmetric representation of sigma(A279105(n)).

1, 3, 7, 11, 15, 23, 31, 35, 39, 47, 55, 59, 63, 71, 79, 83, 95, 107, 111, 119, 127, 131, 143, 159, 167, 175, 179, 191, 199, 207, 215, 223, 239, 251, 255, 263, 279, 287, 299, 311, 319, 323, 335, 351, 359, 383, 391, 395, 399, 407, 415, 419, 431, 439, 447, 455, 467, 479

Offset: 1

Author

Hartmut F. W. Hoft, Dec 06 2016

Keywords

• nonn

Examples

			a(3) = 7 = 2 * A279105(3) - 1;
21 is not in the sequence since 11=(21+1)/2 is not in A174793.
		

Crossrefs

Cf. A174973, A237270, A237271, A237593, A279105.

Programs

Mathematica

a174973Q[n_] := Module[{d=Divisors[n]}, Select[Rest[d] - 2*Most[d], #>0&]=={}]
a279106[n_]:=2*Select[Range[n], a174973Q] - 1
a279106[250] (* sequence data *)

Formula

a(n) = 2 * A279105(n) - 1.