OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MAPLE
isA000079 := proc(n) RETURN( n=1 or numtheory[factorset](n) = {2}) ; end: isA165320 := proc(n) RETURN ( isprime(n) and not isA000079(numtheory[tau](n-1)) and not isA000079(numtheory[tau](n+1)) ) ; end: for n from 1 to 10000 do if isA165320(n) then printf("%d, ", n) ; fi; od: # R. J. Mathar, Sep 18 2009
MATHEMATICA
fQ[n_] := Union[ IntegerQ@# & /@ Log[2, DivisorSigma[0, {n - 1, n + 1}]]] == {False}; Select[ Prime@ Range@ 300, fQ@# &] (* Robert G. Wilson v, Sep 16 2009 *)
Select[Prime[Range[300]], NoneTrue[Log2[DivisorSigma[0, #+{1, -1}]], IntegerQ]&] (* Harvey P. Dale, May 03 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Sep 14 2009
EXTENSIONS
More terms from Robert G. Wilson v and R. J. Mathar, Sep 16 2009
STATUS
approved