

A120397


Minimal number of steps needed to represent a prime >=5 as a sum of at most 3 primes such that all the previous odd primes are represented.


0



1, 2, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 11, 11, 11, 12, 13
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OFFSET

1,2


COMMENTS

This sequence contains probably every natural number, though this should be checked further. Conjecture: Every prime >=5 can be represented as a sum of at most 3 primes, such that all the previous odd primes are represented.


LINKS

Table of n, a(n) for n=1..25.


EXAMPLE

5=2+3>1 step
7=2+2+3=2+5>2 steps
11=2+2+7=3+3+5>2 steps
13=2+11=3+5+5=3+3+7>3 steps
41=2+2+37=3+7+31=5+7+29=5+13+23=5+17+19=11+13+17>6 steps


CROSSREFS

Sequence in context: A093337 A254528 A176044 * A104305 A050506 A155213
Adjacent sequences: A120394 A120395 A120396 * A120398 A120399 A120400


KEYWORD

nonn


AUTHOR

Robin Garcia, Jul 01 2006


STATUS

approved



