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A126105
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Prime(n)^2*prime(n+1)...*prime(a(n)) is the least product of consecutive primes which is abundant. Note that only the first term is squared.
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0
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2, 5, 10, 20, 34, 50, 72, 97, 129, 165, 203, 248, 295, 346, 405, 469, 537, 607, 685, 766, 843, 949, 1049, 1155, 1264, 1376, 1494, 1620, 1754, 1897, 2048, 2193, 2346, 2503, 2669, 2836, 3012, 3193, 3378, 3572, 3770
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| a(3)=10 since x=5^2*7*11*13*17*19*23*29=5391411025 is abundant with sigma(x)=10799308800 and sigma(x)-2*x=16486750.
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MATHEMATICA
| Search[n_] := Module[{}, k =n; While[DivisorSigma[1, Product[ Prime[i], {i, n + 1, k}]*Prime[n]^2] <= 2*Product[Prime[i], {i, n + 1, k}]*Prime[n]^2, k++ ]; k]; Table[Search[i], {i, 1, 15}] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 11 2007
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CROSSREFS
| Cf. A005101, A007684 (a very similar sequence), A007708, A007741.
Sequence in context: A018327 A000099 A039690 * A117486 A000710 A160461
Adjacent sequences: A126102 A126103 A126104 * A126106 A126107 A126108
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KEYWORD
| less,nonn
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AUTHOR
| Walter A. Kehowski (wkehowski(AT)cox.net), Mar 04 2007
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EXTENSIONS
| More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), May 11 2007
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