\\ a(n) is coprime with the next n term (and the floor(n/2) previous terms)
\\ each value is introduced as early as possible

val = Map()	\\ n -> a(n)
idx = []	\\ list of known n's
nxt = 1		\\ next free n

mapput(val, oo, 1)
idx = [oo]

{
	for (v=1, oo,
		if (v==1 || isprime(v),
				\\ prime numbers fill the gaps
				n = nxt,

				\\ find suitable place
				x = 0;	\\ least position with a term not coprime to v
				for (k=1, #idx,
					if (gcd(mapget(val, idx[k]), v)>1,
							x=idx[k],

							\\ all known terms between x+1 and idx[k] are coprime to v
							for (m=2*x+1, oo,
								if (2*m > idx[k],
										break,	\\ might contain some value not coprime to v
									!setsearch(idx, m),
										n=m;
										break (2);
								);
							);
					);
				);
		);

		mapput(val, n, v);
		idx = setunion(idx, [n]);
		while (setsearch(idx, nxt),
			print (nxt " " mapget(val, nxt));
			if (nxt==10 000,
				break (2);
			);
			nxt++;
		);
	);
}

quit