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A015861
Numbers k such that sigma(k) = sigma(k+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
OFFSET
1,1
LINKS
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 *)
PROG
(PARI) is(n)=sigma(n)==sigma(n+3) \\ Charles R Greathouse IV, Mar 09 2014
KEYWORD
nonn
STATUS
approved