|
|
A076530
|
|
Numbers n such that sigma(n) = sigma(n+1) - sigma(n-1).
|
|
7
|
|
|
2, 3, 23, 1967, 3263, 5015, 60455, 1016507, 4420163, 12055511, 14365607, 25726727, 27896423, 66562307, 72764735, 98734967, 175186655, 224868311, 253694927, 288657203, 386668343, 421575407, 504737747, 630645455, 1493547999
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
sigma(24) = 60. sigma(23) = 24. sigma(22) = 36 and 24 = 60 - 36; hence 23 is a term of the sequence.
|
|
MATHEMATICA
|
Select[Range[2, 10^5], DivisorSigma[1, # ] == DivisorSigma[1, # + 1] - DivisorSigma[1, # - 1] &]
Flatten[Position[Partition[DivisorSigma[1, Range[1493548000]], 3, 1], _?(#[[2]] == #[[3]]-#[[1]]&), 1, Heads->False]]+1 (* Harvey P. Dale, Apr 13 2020 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|