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A292564
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Take 1, skip 3 * 1 - 1, take 2, skip 3 * 2 - 1, take 3, skip 3 * 3 - 1, ...
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2
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0, 3, 4, 10, 11, 12, 21, 22, 23, 24, 36, 37, 38, 39, 40, 55, 56, 57, 58, 59, 60, 78, 79, 80, 81, 82, 83, 84, 105, 106, 107, 108, 109, 110, 111, 112, 136, 137, 138, 139, 140, 141, 142, 143, 144, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 210, 211, 212
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = n + floor((sqrt(8*n+1)-1)/2)*(3*floor((sqrt(8*n+1)-1)/2)+1)/2. - Robert Israel, Sep 20 2017
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MAPLE
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seq(seq(2*k^2+k+j, j=0..k), k=0..10); # Robert Israel, Sep 20 2017
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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