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Search: id:A141779
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| 58, 282, 367, 743, 808, 1015, 1141, 1299, 1962, 2109, 2179, 2397, 2501, 3704, 3825, 3912, 3932, 3935, 4016, 4049, 4247, 4327, 4598, 4915, 4977, 5210, 5266, 5396, 5420, 5512, 5562, 5773, 5981, 6031, 6249, 6616, 6984, 7117, 7121, 7304, 7338, 7424, 7653
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OFFSET
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1,1
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COMMENT
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Non prime terms of A120292(n) that are greater than 1 are listed in A141781(n) = {3599, 118477, 210589, 971573, 1164103, 1901959, 2446681, 3230069, ...}.
Note that all listed terms of A141781(n) are semiprime, for example: 3599 = 59*61, 118477 = 257*461, 210589 = 251*839, 971573 = 643*1511.
Conjecture: All non prime terms of A120292(n) that are greater than 1 are semiprime.
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FORMULA
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A141781(n) = A120292( a(n) ).
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MATHEMATICA
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Do[f=Numerator[Abs[(1 - Sum[Prime[k] + 1, {k, 1, n}])/Product[Prime[k] + 1, {k, 1, n}] ]]; If[ !PrimeQ[f]&&!(f==1), Print[{n, f, FactorInteger[f]}]], {n, 1, 8212}]
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CROSSREFS
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Cf. A120292 = Absolute value of numerator of determinant of n X n matrix with elements M[i, j] = Prime[i]/(1+Prime[i]) if i=j and 1 otherwise. Cf. A125716 = Numbers n such that A120292(n) = 1. Cf. A141780 = Numbers n such that A120292(n) is prime. Cf. A141781 = Terms of A120292(n) that are greater than 1 and are not prime; or A120292( A141779(n) ).
Sequence in context: A067914 A051972 A027987 this_sequence A142966 A093258 A017774
Adjacent sequences: A141776 A141777 A141778 this_sequence A141780 A141781 A141782
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KEYWORD
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nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Jul 04 2008
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