A103634 - OEIS

A103634

a(1) = 0; a(n) = the least k such that ((n+1)(n+2)(n+3)...(n+k))/((n-1)(n-2)(n-3)...(n-k)) is an integer (see A092935).

0, 1, 1, 2, 3, 4, 3, 6, 7, 8, 9, 10, 9, 12, 13, 12, 15, 16, 15, 18, 17, 20, 21, 22, 23, 24, 25, 26, 25, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 39, 42, 43, 42, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 63, 66, 67, 68, 69, 70, 71

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,4

LINKS

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

PROG

(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))) }

CROSSREFS

Cf. A092935.

Sequence in context: A330061 A330194 A330105 * A255046 A098596 A217536

Adjacent sequences: A103631 A103632 A103633 * A103635 A103636 A103637

KEYWORD

nonn

AUTHOR

Max Alekseyev, Feb 11 2005

STATUS

approved