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A161959
Smallest composite number which is the sum of n consecutive prime numbers.
0
8, 10, 26, 28, 56, 58, 77, 100, 129, 160, 236, 238, 326, 328, 381, 440, 501, 568, 639, 712, 791, 874, 963, 1060, 1161, 1264, 1371, 1480, 1593, 1720, 1851, 1988, 2127, 2276, 2427, 2584, 2747, 2914, 3087, 3266, 3447, 3638, 3831, 4028, 4227, 4438, 4661, 4888
OFFSET
2,1
FORMULA
a(2n+1) = A007504(2n+1)
a(2n) = A007504(2n) if that value is composite, else A007504(2n+1) - 2.
a(n) ~ n^2 * log(n) / 2.
EXAMPLE
a(6) = 56 = 3 + 5 + 7 + 11 + 13 + 17. (2 + 3 + 5 + 7 + 11 + 13 is prime so not a member of this sequence.)
MATHEMATICA
With[{prs=Prime[Range[500]]}, Table[SelectFirst[Total/@Partition[ prs, n, 1], CompositeQ], {n, 2, 50}]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 15 2019 *)
CROSSREFS
Sequence in context: A182366 A347194 A271313 * A236751 A259713 A096516
KEYWORD
nonn
AUTHOR
Claudio Meller, Jun 22 2009
STATUS
approved