A197640 - OEIS

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A197640

Numbers not representable as the sum of two coprime, squarefree, composite, positive integers.

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

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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