login
A165320
Primes p where neither the number of divisors of p+1 nor the number of divisors of p-1 is a power of 2.
3
17, 19, 97, 149, 163, 197, 199, 241, 293, 307, 337, 349, 449, 491, 523, 557, 577, 739, 773, 811, 881, 883, 991, 1013, 1051, 1061, 1151, 1171, 1249, 1277, 1279, 1423, 1451, 1459, 1471, 1493, 1531, 1549, 1601, 1637, 1667, 1693, 1709, 1733, 1747, 1861, 1949
OFFSET
1,1
LINKS
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
Sequence in context: A272478 A028489 A210242 * A132242 A162873 A174379
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