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A097020 Initial terms of chains consisting of four consecutive integers, for none of which is the value of sigma-function divisible by six. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 4 22:42 EST 2021. Contains 349526 sequences. (Running on oeis4.)