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A091293 a(n) is the smallest x for which the following quotient is an integer: (sigma[x]+...+sigma[x+n-1])/sigma[x+(x+1)+..+(x+n-1)], i.e. sum[sigma[j]]/sigma[sum[j]] for n terms summed up was integer. 2
1, 1, 424, 7, 13980, 2 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

a(7) > 10^8. - David Wasserman (wasserma(AT)spawar.navy.mil), Mar 01 2006

EXAMPLE

n=6: sigma[2]+sigma[3]+..+sigma[7]=3+4+7+6+12+8=40=sigma[2+3+..+7]= sigma[27]=1+3+9+27=40;quotient=1.

Some smaller values:a(9)=7,a(10)=42,a(11)=48957, a(15)=298,a(19)=97.

MATHEMATICA

g[x_, k_] := Apply[Plus, Table[sg[x+j], j, 0, k-1}]]/ sg[Apply[Plus, Table[x+j, j, 0, k-1}]]] Table[fla=1; Do[s=g[n, h]; If[IntegerQ[s]&&Equal[fla, 1], Print[{n, h}]; fla=0], {n, 1, 10000000}], {h, 1, 6}]

CROSSREFS

Cf. A000203, A091287-A091293.

Sequence in context: A206662 A205831 A206408 * A134218 A202772 A091292

Adjacent sequences:  A091290 A091291 A091292 * A091294 A091295 A091296

KEYWORD

hard,nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Feb 17 2004

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Last modified February 15 10:06 EST 2012. Contains 205763 sequences.