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A066134 Numbers from A066112 that are neither square nor twice a square, i.e., are not in A028982 but are in A028983. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A248456 A244178 A131683 * A233682 A233675 A005911

Adjacent sequences:  A066131 A066132 A066133 * A066135 A066136 A066137

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 06 2001

STATUS

approved

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Last modified August 6 12:33 EDT 2020. Contains 336246 sequences. (Running on oeis4.)