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A015861 Numbers n such that sigma(n) = sigma(n + 3). 18
382, 8922, 11935, 31815, 32442, 61982, 123795, 145915, 186615, 271215, 442362, 554715, 560382, 580635, 964535, 1191575, 1243375, 1369302, 1539942, 1642795, 2616702, 3141215, 3299062, 3556035, 3716895, 4201015, 5148294 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..300

MAPLE

A015861:=proc(q) local n;

for n from 1 to q do if sigma(n+3)=sigma(n) then print(n); fi; od; end:

A015861 (10^10); # Paolo P. Lava, Mar 25 2013

MATHEMATICA

Flatten[Position[Partition[DivisorSigma[1, Range[5200000]], 4, 1], {x_, y_, z_, x_}]] (* Harvey P. Dale, Aug 08 2011 *)

Select[Range[6000000], DivisorSigma[1, #]==DivisorSigma[1, # + 3] &] (* Vincenzo Librandi, Mar 10 2014 *)

PROG

(PARI) is(n)=sigma(n)==sigma(n+3) \\ Charles R Greathouse IV, Mar 09 2014

CROSSREFS

Cf. A002961, A007373, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A015883, A181647.

Sequence in context: A172848 A214896 A204861 * A072385 A045122 A064721

Adjacent sequences:  A015858 A015859 A015860 * A015862 A015863 A015864

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified June 4 16:06 EDT 2020. Contains 334828 sequences. (Running on oeis4.)