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A141099 Number of unordered pairs of odd nonprime numbers that sum to 2n. 4
1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 1, 2, 0, 2, 3, 0, 2, 3, 1, 2, 3, 3, 2, 4, 2, 3, 5, 1, 4, 6, 1, 5, 5, 3, 4, 7, 3, 4, 7, 4, 4, 9, 4, 5, 8, 4, 7, 9, 5, 6, 8, 6, 7, 10, 6, 6, 13, 5, 7, 13, 5, 10, 11, 8, 8, 11, 9, 10, 14, 9, 9, 16, 7, 12, 15, 8, 12, 15, 9, 10, 17, 14, 11, 16, 12, 12, 19, 11, 13, 19 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,15

COMMENTS

See A141100 for pairs of odd composite numbers. We have a(n) > 0 except for the 8 values of 2n given in A046458.

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

EXAMPLE

a(18)=3 because 36 = 1+35 = 9+27 = 15+21.

MATHEMATICA

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

CROSSREFS

Cf. A141095, A141097.

Sequence in context: A204329 A111565 A299761 * A127710 A137510 A247303

Adjacent sequences:  A141096 A141097 A141098 * A141100 A141101 A141102

KEYWORD

nonn

AUTHOR

T. D. Noe, Jun 02 2008, Jun 05 2008

STATUS

approved

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Last modified October 18 00:07 EDT 2019. Contains 328135 sequences. (Running on oeis4.)