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Search: id:A087461
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| A087461 |
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Arithmetic mean of n-th and 2n-th primes. |
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+0
3
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| 5, 9, 13, 20, 25, 30, 36, 42, 50, 55, 63, 71, 75, 80, 92, 99, 106, 115, 122, 127, 136, 141, 156, 163, 170, 177, 185, 190, 197, 210, 221, 227, 238, 249, 255, 265, 273, 282, 291, 300, 307, 317, 325, 330, 339, 351, 363, 374, 385, 395, 404, 409, 422, 429, 438, 444
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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A rather sparse subset are primes: 5, 13, 71, = a(2), a(4), a(13).
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FORMULA
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a(n) = (nth prime + 2nth prime)/2
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EXAMPLE
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Series begins with 2nd prime, 3 and 4th prime, 7. Then (3 + 7)/2 = 5.
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CROSSREFS
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Adjacent sequences: A087458 A087459 A087460 this_sequence A087462 A087463 A087464
Sequence in context: A088907 A046586 A023493 this_sequence A057961 A089217 A053411
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KEYWORD
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nonn,easy
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AUTHOR
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Gary W. Adamson (qntmpkt(AT)yahoo.com), Sep 07 2003
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EXTENSIONS
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More terms from Ray Chandler (rayjchandler(AT)sbcglobal.net) and Rick L. Shepherd (rshepherd2(AT)hotmail.com), Sep 09 2003
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