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Search: id:A094756
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| A094756 |
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a(n) = least k>1 such that (1+2+3+...+k) divides (1^n+2^n+3^n +...+k^n). |
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+0
3
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| 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 16, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 16, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 16, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 22, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 16, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 16, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 16, 2, 4, 2, 7, 2, 4, 2, 7, 2, 4, 2, 22, 2, 4, 2, 7, 2, 4
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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Formulae from Don Reble: If N is not divisible by 2, a(N) = 2.
Otherwise, if N is not divisible by 4, a(N) = 4.
Otherwise, if N is not divisible by 12, a(N) = 7.
Otherwise, if N is not divisible by 48, a(N) = 16.
Otherwise, if N is not divisible by 240, a(N) = 22 or 31. (31 if N is divisible by 528=11*48; otherwise 22).
Otherwise, if N is not divisible by 720, a(N) = 37.
Otherwise, if N is not divisible by 11 nor 23, a(N) = 46.
Otherwise, if N is not divisible by 77, a(N) = 58.
Otherwise, if N is not divisible by 13 nor 53, a(N) = 106.
Otherwise, if N is not divisible by 13, a(N) = 157.
Otherwise, if N is not divisible by 41 nor 83, a(N) = 166. ...
That works for N < 29549520 or so. But it is unlikely that any finite description of that kind is complete.
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MATHEMATICA
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f[n_] := Block[{k = 2}, While[ !IntegerQ[ 2Sum[i^n, {i, k}]/(k(k + 1))], k++ ]; k]; Table[ f[n], {n, 50}] (from Robert G. Wilson v Jun 02 2004)
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CROSSREFS
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Cf. A094755.
Sequence in context: A021012 A154120 A021416 this_sequence A110925 A073017 A059866
Adjacent sequences: A094753 A094754 A094755 this_sequence A094757 A094758 A094759
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), May 29 2004
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EXTENSIONS
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Edited and extended by Don Reble and Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 02 2004
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