A015883 Numbers k such that sigma(k) = sigma(k+13).

182, 782, 1965, 2486, 2678, 2685, 12141, 12441, 17342, 21242, 27686, 34905, 35505, 35853, 38662, 38985, 56732, 63578, 104342, 109461, 192933, 198909, 222122, 236966, 245349, 251654, 256322, 261885, 262238, 324441, 333909

Offset

1,1

References

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 182, p. 56, Ellipses, Paris 2008.

Links

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

Maple

A015883:=proc(q) local n;
for n from 1 to q do if sigma(n+13)=sigma(n) then print(n); fi; od; end:
A015883(10^10); # Paolo P. Lava, Mar 25 2013

Mathematica

Select[Range[350000], DivisorSigma[1, #]==DivisorSigma[1, # + 13] &] (* Vincenzo Librandi, Mar 10 2014 *)

Prog

(PARI) is(n)=sigma(n)==sigma(n+13) \\ Charles R Greathouse IV, Mar 09 2014

Crossrefs

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A181647.

Sequence in context: A056091 A272361 A158553 * A043463 A047636 A157205

Adjacent sequences: A015880 A015881 A015882 * A015884 A015885 A015886

Keyword

nonn

Author

Robert G. Wilson v

Extensions

Corrected by T. D. Noe, Oct 31 2006

Status

approved