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A096102 a(1) = 1, a(2) = 3; for n > 2: a(n) = smallest (odd) number not occurring earlier such that the sum of each section of odd length >=3 is prime. 0
1, 3, 7, 9, 21, 13 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
If 1, 3, 7, 13 are taken (rather arbitrarily) as starting terms, then the continuation is 17, 31, 11, 25, 5, 37, 341, 163, 647, 571, 989, 3451, 17669, 206413, 6767, 252289, but no number < 10000000 is suited to continue this sequence further.
There are no further terms. For k to qualify as next term the sums 21+13+k, 7+9+21+13+k and 1+3+7+9+21+13+k have to be prime. One of these sums however is divisible by 3, since 34+k = k+1 (mod 3), 50+k = k+2 (mod 3) and 54+k = k (mod 3). - Klaus Brockhaus, Jul 02 2004
LINKS
EXAMPLE
1+3+7 = 11, 3+7+9 = 19, 7+9+21 = 37, 9+21+13 = 43, 1+3+7+9+21 = 41, 3+7+9+21+13 = 53 are all prime.
CROSSREFS
Sequence in context: A304128 A304539 A306124 * A316157 A045797 A118555
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Jun 24 2004
EXTENSIONS
Edited and corrected by Klaus Brockhaus, Jun 29 2004
STATUS
approved

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Last modified March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)