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Search: id:A154891
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| 1, 2, 4, 9, 12, 21, 24, 30, 42, 45, 57, 60, 75, 84, 90, 105, 135, 150, 165, 195, 210, 255, 315, 330, 390, 420, 525, 630, 735, 825, 840, 945, 1050, 1155, 1365, 1575, 1680, 1785, 1995, 2100, 2145, 2205, 2310, 2625, 2730, 3045, 3255, 3465, 3990
(list; graph; listen)
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OFFSET
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1,2
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MAPLE
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A008578 := proc(n) RETURN( n=1 or isprime(n) ) ; end : A154804 := proc(n) local a, d; a := 0 ; for d from 1 to n-1 do if A008578(n-d) and A008578(n+d) then a := a+1; fi; od: a ; end: a804 := [seq(A154804(n), n=1..4000)] ; r := RECORDS(a804)[2] ; [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 14 2009]
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CROSSREFS
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Cf. A008578, A154804, A154720, A154721, A154799.
Sequence in context: A088901 A111302 A092530 this_sequence A139557 A103690 A098009
Adjacent sequences: A154888 A154889 A154890 this_sequence A154892 A154893 A154894
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KEYWORD
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nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), Feb 01 2009
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 14 2009
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