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A197640 Numbers not representable as the sum of two coprime, squarefree, composite, positive integers. 0
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 50, 51, 52, 54, 56, 58, 60, 62, 63, 64, 66, 70, 72, 75, 78, 80, 82, 84, 88, 90, 96, 100, 102, 105, 108, 110, 114, 120, 126, 130, 132, 138, 140, 144, 150, 156, 168, 180, 190, 204, 210, 240, 270, 330, 420 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(87) = 420 is probably the last term.

LINKS

Table of n, a(n) for n=1..87.

PROG

(PARI) is(n)=for(k=6, n\2, if(gcd(k, n-k)==1&&!isprime(k)&&!isprime(n-k)&&issquarefree(k)&&issquarefree(n-k), return(0))); 1 \\ Charles R Greathouse IV, Oct 18 2011

CROSSREFS

Cf. A197629, A096076.

Sequence in context: A087143 A080683 A174228 * A246099 A280865 A124231

Adjacent sequences:  A197637 A197638 A197639 * A197641 A197642 A197643

KEYWORD

nonn

AUTHOR

Jason Holland, Oct 16 2011

STATUS

approved

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Last modified April 9 10:51 EDT 2020. Contains 333348 sequences. (Running on oeis4.)