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Search: id:A130216
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| A130216 |
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a(0) = 3; a(n) = a(n-1) + (number of multiples of 3 so far in the sequence). |
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+0
1
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| 3, 4, 5, 6, 8, 10, 12, 15, 19, 23, 27, 32, 37, 42, 48, 55, 62, 69, 77, 85, 93, 102, 112, 122, 132, 143, 154, 165, 177, 190, 203, 216, 230, 244, 258, 273, 289, 305, 321, 338, 355, 372, 390, 409, 428, 447, 467, 487, 507, 528, 550, 572, 594, 617, 640, 663, 687, 712
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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See A007980 for the same construction with multiples of 2.
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FORMULA
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G.f.: -(3*x^8-2*x^7+x^4-2*x+3) / (x^9-2*x^8+x^7-x^2+2*x-1). [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 12 2009]
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EXAMPLE
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3,4,5,6,8,10,12,15: next term is 19 which is 15 + 4 previous terms divisible by 3 (they are 3,6,12,15)
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MAPLE
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a:= proc(n) local m, r; m:= iquo (n, 7, 'r'); (3+21*m+6*r) *m/2 +[3, 4, 5, 6, 8, 10, 12][r+1] end: seq (a(n), n=0..80); [From Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 12 2009]
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CROSSREFS
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Sequence in context: A026512 A026506 A051916 this_sequence A120162 A002859 A062514
Adjacent sequences: A130213 A130214 A130215 this_sequence A130217 A130218 A130219
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KEYWORD
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easy,nonn
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AUTHOR
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Eric Angelini (eric.angelini(AT)kntv.be), Aug 05 2007
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EXTENSIONS
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More terms from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 12 2009
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