A074120 - OEIS

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A074120

Group successively larger composite numbers so that the sum of the n-th group is a multiple of n. Sequence gives the sum of the terms in the n-th group.

4, 6, 27, 12, 45, 18, 63, 24, 270, 330, 198, 780, 2314, 644, 1800, 3600, 3808, 3150, 6479, 3500, 7140, 2662, 2438, 936, 5175, 6526, 1431, 8596, 12586, 8730, 7812, 20768, 3663, 38488, 13020, 16848, 1998, 10830, 21099, 39840, 4715, 60732, 15953

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

EXAMPLE

(4), (6), (8, 9, 10), (12), (14, 15, 16), (18), (20, 21, 22), (24), (25, 26, 27, 28, 30, 32, 33, 34, 35), (36, 38, 39, 40, 42, 44, 45, 46), (48, 49, 50, 51), ...

MATHEMATICA

NextComposite[n_] := Block[{k = n + 1}, While[PrimeQ[k], k++ ]; k]; a = {}; k = 1; Do[s = 0; While[k = NextComposite[k]; s = s + k; !IntegerQ[s/n], ]; a = Append[a, s], {n, 1, 45}]; a

CROSSREFS

Cf. A002808, A074128, A074121, A074122 A074123.

Sequence in context: A123873 A193689 A099941 * A054265 A105409 A109934

Adjacent sequences: A074117 A074118 A074119 * A074121 A074122 A074123

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Aug 27 2002

EXTENSIONS

Edited, corrected and extended by Robert G. Wilson v, Aug 29 2002

STATUS

approved