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A231089 Initial members of abundant quadruplets, i.e., values of n such that (n, n+2, n+4, n+6) are all abundant numbers. 7
348, 1998, 2208, 2748, 2988, 2990, 3006, 3246, 3708, 3846, 4506, 4728, 4730, 5166, 6228, 7068, 7206, 7908, 8886, 9348, 9588, 9724, 9726, 11406, 13746, 14208, 14766, 17148, 17988, 18126, 18588, 18828, 18844, 18846, 19548, 20148, 20478, 21486, 22188, 22984 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Shyam Sunder Gupta, Table of n, a(n) for n = 1..5000

EXAMPLE

348, 350, 352, 354 are abundant, thus the smallest number is listed.

MATHEMATICA

AbundantQ[n_] := DivisorSigma[1, n] > 2n; m = 0; a = {}; Do[If[AbundantQ[n], m = m + 1; If[m > 3, AppendTo[a, n - 6]], m = 0], {n, 2, 1000000, 2}]; a

SequencePosition[Table[If[DivisorSigma[1, n]>2n, 1, 0], {n, 23000}], {1, _, 1, _, 1, _, 1}][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 02 2018 *)

PROG

(PARI) is(n)=sigma(n, -1)>2 && sigma(n+2, -1)>2 && sigma(n+4, -1)>2 && sigma(n+6, -1)>2 \\ Charles R Greathouse IV, Feb 21 2017

CROSSREFS

Cf. A005101, A108926, A231086, A231088, A231090, A231092, A231093.

Sequence in context: A275237 A129642 A304837 * A237318 A237724 A054467

Adjacent sequences:  A231086 A231087 A231088 * A231090 A231091 A231092

KEYWORD

nonn

AUTHOR

Shyam Sunder Gupta, Nov 03 2013

STATUS

approved

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Last modified February 20 04:49 EST 2020. Contains 332063 sequences. (Running on oeis4.)