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Search: id:A115404
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| A115404 |
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Numbers n such that n^4+1 is a 4-almost prime (product of four primes). |
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| 43, 59, 77, 79, 83, 85, 95, 111, 127, 137, 147, 155, 178, 179, 185, 202, 221, 223, 227, 229, 233, 239, 241, 247, 249, 253, 261, 263, 270, 271, 273, 285, 287, 297, 314, 331, 338, 341, 342, 357, 359, 387, 389, 393, 395, 401, 408, 413, 421, 427, 433, 435, 437
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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n^4+1=p*q*r*s where p, q, r, s are primes (not necessarily distinct).
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EXAMPLE
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43 is OK because 43^4+1=3418802=2*17*193*521 (product of four primes).
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MATHEMATICA
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Select[Range[500], Sum[FactorInteger[ #^4 + 1][[i]][[2]], {i, 1, Length[FactorInteger[ #^4 + 1]]}] == 4 &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Mar 09 2006
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CROSSREFS
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Cf. A014613 = 4-almost primes.
Sequence in context: A166491 A127880 A078132 this_sequence A033223 A064508 A102540
Adjacent sequences: A115401 A115402 A115403 this_sequence A115405 A115406 A115407
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KEYWORD
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nonn
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Mar 08 2006
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