1,4

Table of n, a(n) for n=1..73.

(PARI) { a(n) = local(p, q, r); p=1; q=1; for(k=1, n, p*=n+k; q*=n-k; r=gcd(p, q); p\=r; q\=r; if(q==1, return(k))) }

Cf. A092935.

Sequence in context: A330061 A330194 A330105 * A255046 A098596 A217536

Adjacent sequences: A103631 A103632 A103633 * A103635 A103636 A103637

nonn

Max Alekseyev, Feb 11 2005

approved