A097020 Initial terms of chains consisting of four consecutive integers, for none of which is the value of sigma-function divisible by six.

1, 241, 576, 721, 1249, 2449, 12481, 23761, 40897, 65521, 120049, 126001, 128016, 167041, 186049, 211248, 211249, 344449, 374976, 406801, 417697, 451249, 607201, 647521, 665856, 708049, 746641, 766321, 1039681, 1068721, 1092241, 1146096

Offset

0,2

Comments

It is believed that in all of such quadruples remainder 3 always arises.

Links

Table of n, a(n) for n=0..31.

Example

n=241: sigma-s for {241,242,243,244} are {242,399,364,434}
whose remainders modulo 6 are {2,3,4,2}.

Mathematica

SequencePosition[Table[If[Divisible[DivisorSigma[1, n], 6], 0, 1], {n, 12*10^5}], {1, 1, 1, 1}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 21 2017 *)

Crossrefs

Cf. A084301.

Sequence in context: A142233 A142275 A260605 * A163623 A142856 A204355

Adjacent sequences: A097017 A097018 A097019 * A097021 A097022 A097023

Keyword

nonn

Author

Labos Elemer, Aug 23 2004

Extensions

Definition rephrased by Harvey P. Dale, Oct 21 2017

Status

approved