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Search: id:A134155
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| A134155 |
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a(n)= 1 + 21 n + 168 n^2 + 588 n^3 + 1029 n^4 : sum[k^6]/sum[k^2], {k, 1, 7n + 1}]. |
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+0
1
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| 1, 1807, 21883, 100801, 303829, 720931, 1466767, 2680693, 4526761, 7193719, 10895011, 15868777, 22377853, 30709771, 41176759, 54115741, 69888337, 88880863, 111504331, 138194449, 169411621, 205640947, 247392223, 295199941
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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A000540(n) is divisible by A000330(n) if and only n is congruent to 1 mod 7
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FORMULA
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1) 3(7n + 1)^4 + 6(7n + 1)^2 - 3 (7n + 1) + 1)/7 2) a(n) = sum[k^6]/sum[k^2], {k, 1, 7n + 1}]
G.f.: -(1+1802*x+12858*x^2+9446*x^3+589*x^4)/(-1+x)^5. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 14 2007
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MATHEMATICA
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1) Table[1 + 21 n + 168 n^2 + 588 n^3 + 1029 n^4, {n, 0, 50}] 2) Table[Sum[k^6, {k, 1, 7n + 1}]/Sum[k^2, {k, 1, 7n + 1}], {n, 0, 50}] (*Artur Jasinski*)
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CROSSREFS
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Cf. A000330, A000540, A119617, A134153, A134154.
Adjacent sequences: A134152 A134153 A134154 this_sequence A134156 A134157 A134158
Sequence in context: A020402 A035868 A122477 this_sequence A058954 A124073 A031934
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Oct 10 2007
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