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A141095 Number of unordered pairs of coprime nonprime numbers that sum to 2n. 7
1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 2, 1, 0, 1, 0, 1, 2, 0, 1, 2, 0, 1, 3, 0, 1, 4, 1, 1, 1, 0, 3, 4, 1, 0, 4, 0, 4, 3, 0, 4, 5, 1, 1, 3, 1, 4, 6, 0, 0, 4, 1, 6, 6, 1, 5, 7, 1, 5, 3, 0, 8, 7, 0, 0, 10, 3, 9, 9, 0, 6, 5, 2, 8, 5, 2, 9, 10, 1, 5, 11, 2, 9, 12, 0, 3, 12, 4, 11, 5, 2, 12, 9, 1, 4, 14 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,17

COMMENTS

Nonprime numbers are 1 and the composite numbers. See A141097 for pairs of coprime composite numbers. It appears that a(n) > 0 except for the 26 values of 2n given in A141096.

LINKS

T. D. Noe, Table of n, a(n) for n=1..10000

Carlos Rivera, Conjecture 33: The Goldbach Temptation

EXAMPLE

a(17)=2 because 34 = 1+33 = 9+25.

MATHEMATICA

Table[cnt=0; Do[If[GCD[2n-i, i]==1 && !PrimeQ[i] && !PrimeQ[2n-i], cnt++ ], {i, 1, n, 2}]; cnt, {n, 100}]

CROSSREFS

Cf. A141099, A141100.

Sequence in context: A307776 A050317 A325223 * A175599 A179759 A257260

Adjacent sequences:  A141092 A141093 A141094 * A141096 A141097 A141098

KEYWORD

nonn,look

AUTHOR

T. D. Noe, Jun 02 2008

STATUS

approved

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Last modified October 23 23:51 EDT 2019. Contains 328379 sequences. (Running on oeis4.)