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A015877 Numbers n such that sigma(n) = sigma(n + 9). 15
14, 16, 46, 446, 1146, 26766, 35805, 143605, 179086, 185946, 437745, 1187725, 1194646, 1327086, 1746946, 2201806, 2893605, 3003385, 3574725, 3730125, 4053586, 4928385, 5715325, 6220305, 7507946, 9423645, 9897186 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..200

MAPLE

A015877:=proc(q) local n;

for n from 1 to q do if sigma(n+9)=sigma(n) then print(n); fi; od; end:

A015877(10^10); # Paolo P. Lava, Mar 25 2013

MATHEMATICA

Select[Range[10000000], DivisorSigma[1, #]==DivisorSigma[1, # + 9] &] (* Vincenzo Librandi, Mar 10 2014 *)

Position[Partition[DivisorSigma[1, Range[10^7]], 10, 1], _?(#[[1]] == #[[10]]&), {1}, Heads->False]//Flatten (* Harvey P. Dale, Aug 25 2016 *)

PROG

(PARI) is(n)=sigma(n)==sigma(n+9) \\ Charles R Greathouse IV, Mar 09 2014

CROSSREFS

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015880, A015881, A015882, A015883, A181647.

Sequence in context: A305885 A224402 A067844 * A192290 A152010 A243750

Adjacent sequences:  A015874 A015875 A015876 * A015878 A015879 A015880

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified March 7 19:13 EST 2021. Contains 341928 sequences. (Running on oeis4.)