A015881 Numbers k such that sigma(k) = sigma(k+11).

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

Offset: 1

Author

Robert G. Wilson v

Keywords

• nonn

Links

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

Crossrefs

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

Programs

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 *)

PARI

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