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 A066868 Least natural number k such that n + sum{i=1,...,k} Safe_Prime[i] is prime, if such k exists; = 0 otherwise. 0
 2, 1, 10, 5, 2, 1, 2, 1, 12, 5, 2, 1, 4, 1, 4, 5, 2, 1, 2, 3, 4, 7, 12, 1, 2, 1, 4, 7, 2, 3, 2, 1, 4, 5, 2, 1, 4, 1, 6, 17, 2, 1, 4, 3, 6, 5, 2, 1, 2, 3, 4, 11, 12, 1, 2, 1, 4, 5, 2, 3, 2, 1, 4, 5, 14, 1, 2, 1, 10, 5, 2, 7, 10, 1, 6, 7, 2, 1, 8, 3, 4, 7, 26, 1, 2, 3, 6, 5, 2, 3, 2, 1, 4, 11, 2, 1, 2, 1, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Safe_Prime[i] denotes the i-th safe prime (A005385). Conjecture: a(n) is nonzero for all n, so every n can be represented as the difference between a prime and a partial sum of the safe primes series. See A066753 for a similar conjecture. LINKS EXAMPLE 4 + (5 + 7 + 11 + 23 + 47) = 97, a prime and 5 consecutive safe primes, starting from the first safe prime 5, are needed to achieve this. Hence a(4) = 5. CROSSREFS Cf. A005385, A066753. Sequence in context: A126450 A235608 A112333 * A193900 A319373 A143172 Adjacent sequences:  A066865 A066866 A066867 * A066869 A066870 A066871 KEYWORD nonn AUTHOR Joseph L. Pe, Jan 21 2002 STATUS approved

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Last modified June 5 16:30 EDT 2020. Contains 334852 sequences. (Running on oeis4.)