A015861 Numbers k such that sigma(k) = sigma(k+3).

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

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

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

Crossrefs

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

Programs

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 *)
SequencePosition[DivisorSigma[1,Range[5150000]],{x_,,,x_}][[;;,1]] (* Harvey P. Dale, Dec 01 2024 *)

PARI

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