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A114964
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a(n) = n^2 + 30.
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6
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30, 31, 34, 39, 46, 55, 66, 79, 94, 111, 130, 151, 174, 199, 226, 255, 286, 319, 354, 391, 430, 471, 514, 559, 606, 655, 706, 759, 814, 871, 930, 991, 1054, 1119, 1186, 1255, 1326, 1399, 1474, 1551, 1630, 1711, 1794, 1879, 1966, 2055, 2146, 2239, 2334, 2431
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OFFSET
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0,1
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COMMENTS
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x^2 + 30 != y^n for all x,y and n > 1, so this is a subsequence of A007916.
This is the case k=5 of the identity n^2 + k*(k+1) = ( Sum_{i=-k..k} (n+i)^3 ) / ( (2*k+1)*n ).
The old name of this sequence was: Numbers of the form x^2 + 30. Also numbers that are not a perfect power.
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LINKS
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FORMULA
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Sum_{n>=0} 1/a(n) = (1 + sqrt(30)*Pi*coth(sqrt(30)*Pi))/60.
Sum_{n>=0} (-1)^n/a(n) = (1 + sqrt(30)*Pi*cosech(sqrt(30)*Pi))/60. (End)
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EXAMPLE
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11*4*a(4) = (-1)^3 + 0^3 + 1^3 + 2^3 + 3^3 + 4^3 + 5^3 + 6^3 + 7^3 + 8^3 + 9^3 = 2024. - Bruno Berselli, May 12 2014
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MATHEMATICA
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PROG
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(PARI) g(n, p) = for(x=0, n, y=x^2+p; print1(y", "));
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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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EXTENSIONS
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STATUS
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approved
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