A097704 Elements of A097703 not of form 3k + 1.

12, 24, 60, 62, 84, 87, 122, 137, 144, 162, 171, 180, 212, 237, 264, 269, 287, 302, 312, 318, 362, 387, 416, 420, 422, 423, 437, 462, 465, 480, 512, 537, 563, 587, 591, 612, 662, 665, 684, 687, 710, 722, 737, 759, 762, 786, 812, 837, 840, 857, 887, 902

Offset

1,1

Comments

Conjecture: "most" of the terms also belong to [(A067778-1)/2]. Exceptions are {302, 2117, ...}. In other words, most terms satisfy: GCD(2n+1, numerator(B(4n+2))) is not squarefree, with B(n) the Bernoulli numbers.

Links

Table of n, a(n) for n=1..52.

Mathematica

usigma[n_] := Block[{d = Divisors[n]}, Plus @@ Select[d, GCD[ #, n/# ] == 1 &]]; Complement[ Range[1017], Table[3k - 2, {k, 340}], (Select[ Range[220000], DivisorSigma[1, # ] == 2usigma[ # ] &] - 108)/216] (* Robert G. Wilson v, Aug 28 2004 *)

Crossrefs

Sequence in context: A247944 A346865 A123980 * A289132 A348716 A098585

Adjacent sequences: A097701 A097702 A097703 * A097705 A097706 A097707

Keyword

nonn

Author

Ralf Stephan, Aug 26 2004

Status

approved