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A015916
Numbers k such that sigma(k) + 10 = sigma(k+10).
7
3, 7, 13, 19, 31, 37, 43, 61, 73, 79, 97, 103, 127, 139, 157, 163, 181, 223, 229, 241, 271, 283, 307, 337, 349, 373, 379, 409, 421, 433, 439, 457, 499, 547, 577, 607, 631, 643, 673, 691, 709, 733, 751, 787, 811, 829, 853, 877, 919, 937, 967, 1009
OFFSET
1,1
COMMENTS
Different from A023203. Below 1000000 the only composite number here is 195556: sigma(195556) + 10 = 342230 + 10 = sigma(195566). - Labos Elemer, May 23 2000
LINKS
MATHEMATICA
Select[Range[2000], DivisorSigma[1, #] + 10==DivisorSigma[1, # + 10] &] (* Vincenzo Librandi, Mar 10 2014 *)
Select[Partition[DivisorSigma[1, Range[1100]], 11, 1], #[[1]]+10==#[[-1]]&][[All, 1]]-1 (* Harvey P. Dale, May 20 2021 *)
CROSSREFS
KEYWORD
nonn
STATUS
approved