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A015867 Numbers k such that sigma(k) = sigma(k+7). 16
10, 62, 188, 362, 759, 1178, 1214, 1431, 1442, 1598, 1695, 1748, 2235, 3495, 6699, 9338, 9945, 11438, 13695, 18795, 20727, 26199, 26631, 30548, 35438, 53751, 79826, 79827, 89378, 103887, 114231, 122738, 132111, 135506, 138135 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 62, p. 22, Ellipses, Paris 2008.

LINKS

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

MAPLE

A015867:=proc(q) local n;

for n from 1 to q do if sigma(n+7)=sigma(n) then print(n); fi; od; end:

A015867(10^10); # Paolo P. Lava, Mar 25 2013

MATHEMATICA

Select[Range[140000], DivisorSigma[1, #]==DivisorSigma[1, # + 7] &] (* Vincenzo Librandi, Mar 10 2014 *)

PROG

(PARI) is(n)=sigma(n)==sigma(n+7) \\ Charles R Greathouse IV, Mar 09 2014

CROSSREFS

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015876, A015877, A015880, A015881, A015882, A015883, A181647.

Sequence in context: A025574 A301383 A321386 * A297863 A298130 A106629

Adjacent sequences:  A015864 A015865 A015866 * A015868 A015869 A015870

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved

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Last modified August 18 13:09 EDT 2022. Contains 356212 sequences. (Running on oeis4.)