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Search: id:A090481
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| A090481 |
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Primes p such that tau(p-1)+tau(p+1) is larger than for any previous term. (Smallest prime sandwiched between more composite numbers). |
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+0
4
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| 2, 3, 5, 7, 11, 17, 19, 29, 41, 71, 179, 181, 239, 419, 701, 839, 881, 1259, 1871, 2161, 2521, 4159, 5039, 7561, 10079, 13441, 13859, 20161, 22679, 30241, 35281, 45361, 55439, 65519, 110879, 138599, 151201, 166319, 226799, 262079, 327599, 332641
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OFFSET
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1,1
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EXAMPLE
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17 follows 11 and 13 is not a term as tau(10) + tau(12) = tau(12) + tau(14) = 10.
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MATHEMATICA
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a = {}; t = 0; Do[p = Prime[n]; s = DivisorSigma[0, p - 1] + DivisorSigma[0, p + 1]; If[s > t, t = s; AppendTo[a, p]], {n, 1, 10^5}]; a (from Robert G. Wilson v Dec 04 2003)
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CROSSREFS
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Cf. A090482, A000005.
Sequence in context: A095365 A042989 A089084 this_sequence A164641 A058982 A040069
Adjacent sequences: A090478 A090479 A090480 this_sequence A090482 A090483 A090484
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Dec 02 2003
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 04 2003
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