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A015881 Numbers k such that sigma(k) = sigma(k+11). 15
28, 154, 466, 874, 958, 1054, 2266, 2878, 11505, 12754, 14674, 17974, 21154, 21778, 29223, 29535, 31725, 32714, 39658, 43186, 48004, 52018, 62338, 70198, 126795, 132783, 163251, 164818, 207603, 212938, 221595, 272685, 274527 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

MAPLE

A015881:=proc(q) local n;

for n from 1 to q do if sigma(n+11)=sigma(n) then print(n); fi; od; end:

A015881(10^10); # Paolo P. Lava, Mar 25 2013

MATHEMATICA

Select[Range[300000], DivisorSigma[1, #]==DivisorSigma[1, # + 11] &] (* Vincenzo Librandi, Mar 10 2014 *)

Position[Partition[DivisorSigma[1, Range[300000]], 12, 1], _?(First[#]== Last[#]&), 1, Heads->False]//Flatten (* Harvey P. Dale, Aug 20 2017 *)

PROG

(PARI) is(n)=sigma(n)==sigma(n+11) \\ Charles R Greathouse IV, Mar 09 2014

CROSSREFS

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015882, A015883, A181647.

Sequence in context: A271636 A188778 A002593 * A026910 A172220 A255151

Adjacent sequences:  A015878 A015879 A015880 * A015882 A015883 A015884

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified August 18 11:47 EDT 2022. Contains 356212 sequences. (Running on oeis4.)