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Search: id:A114410
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| 1, 3, 6, 16, 37, 147, 420, 2290, 7477, 50487, 200910, 1534220, 7099871, 61765581, 301088574, 2870376944, 15554495573, 167142509403, 940873745772, 9581390534082, 64516308316281, 695274033862911, 5035132538656632
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OFFSET
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0,2
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COMMENT
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The cumulative sum is prime for a(2) = 3, a(4) = 37, a(8) = 7477, a(12) = 7099871, a(16) = 15554495573. The sum a(n) is semiprime for n = 2, 9.
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FORMULA
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a(n) = 0## + 1## + ... + n##, where n## = p(n)*(n-2)##, where p(n) is the n-th prime.
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EXAMPLE
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n 0## + ... + n##
0 1.
1 1+2 = 3.
2 1+2+3 = 6.
3 1+2+3+10 = 16.
4 1+2+3+10+21 = 37.
5 1+2+3+10+21+110 = 147.
6 1+2+3+10+21+110+273 = 420.
7 1+2+3+10+21+110+273+1870 = 2290.
8 1+2+3+10+21+110+273+1870+5187 = 7477.
9 1+2+3+10+21+110+273+1870+5187+ 43010 = 50487.
10 1+2+3+10+21+110+273+1870+5187+ 43010 + 150423 = 200910.
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CROSSREFS
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Cf. A079078.
Sequence in context: A072824 A089406 A027852 this_sequence A096588 A073079 A143560
Adjacent sequences: A114407 A114408 A114409 this_sequence A114411 A114412 A114413
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Feb 12 2006
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