OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Brian Hayes, Does having prime neighbors make you more composite?, Bit-Player Article, Nov 04 2021
EXAMPLE
MATHEMATICA
midQ[n_] := PrimeQ[n-1] && PrimeQ[n+1]; DivisorSigma[0, Select[Range[3000], midQ]] (* Amiram Eldar, Nov 03 2019 *)
DivisorSigma[0, #]&/@(Mean/@Select[Partition[Prime[Range[500]], 2, 1], #[[2]]- #[[1]] == 2&]) (* Harvey P. Dale, Nov 07 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 29 2002
STATUS
approved