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A027916
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Least k such that 1+2+...+k >= E{1,2,...,n}, where E = 2nd elementary symmetric function.
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1
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2, 5, 8, 13, 19, 25, 33, 42, 51, 62, 74, 86, 100, 115, 130, 147, 165, 183, 203, 224, 245, 268, 292, 316, 342, 369, 396, 425, 455, 485, 517, 550, 583, 618, 654, 690, 728, 767, 806, 847, 889, 931, 975, 1020, 1065, 1112, 1160, 1208, 1258, 1309, 1360, 1413, 1467
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OFFSET
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2,1
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LINKS
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FORMULA
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G.f.: x^2 * (x+2) / ((1-x^3)*(1-x)^2).
Conjecture: a(n) = n + (n^2 mod 3) + a(n-1). - Jon Maiga, Aug 02 2019
a(n) = ceiling((1/2)*(sqrt(3*n^4 + 2*n^3 - 3*n^2 - 2*n + 3)/sqrt(3) - 1)) = (3*n+4)*(n-1)/6 + ((n+2) mod 3)/3. - Rick Mabry, Jul 01 2023
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MATHEMATICA
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Table[Total[Table[IntegerExponent[2^(n - k) 4^k, 8], {k, 0, n}]], {n, 2, 100}] (* Fred Daniel Kline, Jun 05 2012 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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