A066134 Numbers from A066112 that are neither square nor twice a square, i.e., are not in A028982 but are in A028983.

48, 180, 245, 432, 500, 605, 931, 980, 1200, 1280, 1620, 1805, 2205, 2352, 2420, 3380, 3724, 3888, 3920, 4500, 4655, 5445, 5780, 5808, 6125, 6845, 7203, 7220, 7936, 8112, 8379, 8405, 8820, 9072, 9251, 9680, 10580, 10800, 11520, 11760, 12500

Offset

1,1

Links

Harry J. Smith, Table of n, a(n) for n=1..1000

Example

180 is neither square nor 2*square, but sigma_4(180)/sigma_2(180) = 1135275414/49686 = 22849 = 73*313.

Prog

(PARI) { n=0; for (m=1, 10^9, if (issquare(m) || issquare(m/2), next); if (frac(f=sigma(m, 4)/sigma(m, 2)), next); if (!isprime(f), write("b066134.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Feb 02 2010

Crossrefs

Cf. A001157, A001159, A028982, A028983, A046871, A066109-A066112.

Sequence in context: A346293 A244178 A131683 * A233682 A233675 A005911

Adjacent sequences: A066131 A066132 A066133 * A066135 A066136 A066137

Keyword

nonn

Author

Labos Elemer, Dec 06 2001

Status

approved