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Search: id:A134506
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| A134506 |
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Number of 2 X 2 singular integer matrices with elements from {1,...,n}. |
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+0
3
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| 1, 6, 15, 32, 49, 86, 111, 160, 209, 278, 319, 432, 481, 582, 703, 832, 897, 1078, 1151, 1360, 1537, 1702, 1791, 2096, 2257, 2454, 2671, 2976, 3089, 3510, 3631, 3952, 4241, 4502, 4831, 5360, 5505, 5798, 6143, 6704, 6865, 7478, 7647, 8144, 8721, 9078, 9263
(list; graph; listen)
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OFFSET
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1,2
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MATHEMATICA
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a = {}; For[n = 2, n < 50, n++, s = 0; For[j = 1, j < n + 1, j++, For[c = 1, c < n + 1, c++, s = s + Length[Select[Divisors[c*j], # < n + 1 && c*j/# < n + 1 &]]]]; AppendTo[a, s]]; a - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Feb 06 2008
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CROSSREFS
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Cf. number of 2 X 2 singular integer matrices with elements from {0, ..., n}: A059306.
Adjacent sequences: A134503 A134504 A134505 this_sequence A134507 A134508 A134509
Sequence in context: A011886 A056497 A092411 this_sequence A143274 A121666 A118734
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KEYWORD
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nonn,nice
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AUTHOR
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Graziano Aglietti (mg5055(AT)mclink.it), Jan 20 2008, Feb 04 2008
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Feb 06 2008
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