login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=0..98.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 18 04:50 EDT 2019. Contains 326072 sequences. (Running on oeis4.)