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A079841 Duplicate of A069869. 0
0, 11, 3, 211, 2111, 0, 112111, 1111211, 0, 11131111, 1121111111, 0, 111211111111, 2111111111111, 0, 31111111111111, 212111111111111, 0, 1111111111111111111, 2111111111111111111, 0, 111111111111111121111, 11111111111111111111111, 0, 211111111111111111111111 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Name was: Largest prime that is a concatenation of partitions of n; or 0 if no such number exists.

a(1) = a(3k+3)= 0. Conjecture: a(n) is nonzero for all other values of n.

When a repunit (10^n - 1)/9 = A002275(n) is a repunit prime (A004022) then a(n) = A004022(n), as is the case for n = 2, 19, 23, 317, 1031, etcetera. See also: A000041 number of partitions of n (the partition numbers). For an a(n) = 0 one must have checked up to A000041 partitions for primality and chosen the maximum, or otherwise eliminated all possibilities by proof. E.g. a(9) = 0 as all integers in the partition must be single digits, whose sum must be 9, hence any such concatenation must be divisible by 9. - Jonathan Vos Post, Mar 20 2006

LINKS

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

EXAMPLE

a(4) = 211 though 31 and 13 are also prime.

CROSSREFS

Cf. A000040, A000041, A004022, A002275.

Sequence in context: A038317 A157781 A069869 * A110782 A088073 A010187

Adjacent sequences:  A079838 A079839 A079840 * A079842 A079843 A079844

KEYWORD

dead

AUTHOR

Amarnath Murthy, Feb 16 2003

EXTENSIONS

More terms from Jonathan Vos Post, Mar 20 2006

STATUS

approved

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Last modified December 21 16:36 EST 2014. Contains 252324 sequences.