A243045 Largest number k such that k*n/(k+n) and k*n/(k-n) are integers or 0 if no such number exists.

0, 0, 6, 12, 0, 12, 0, 24, 18, 15, 0, 60, 0, 0, 60, 48, 0, 36, 0, 60, 42, 0, 0, 168, 0, 0, 54, 84, 0, 120, 0, 96, 66, 0, 210, 180, 0, 0, 78, 360, 0, 105, 0, 132, 180, 0, 0, 336, 0, 75, 102, 156, 0, 108, 66, 168, 114, 0, 0, 660, 0, 0, 504, 192, 0, 132, 0, 204, 138, 420, 0, 504

Offset

1,3

Links

Antti Karttunen, Table of n, a(n) for n = 1..10080

Example

k*3/(k-3) and k*3/(k+3) are integers only for k=6. Thus since 6 is the largest k-value, a(3) = 6.

Prog

(PARI) a(n)=for(k=-n*(n+1), 0, if(-k!=n, if((-k*n)/(-k+n)==0&&(-k*n)/(-k-n)==0, return(-k))))
n=1; while(n<100, print1(a(n), ", "); n+=1)

Crossrefs

Cf. A243017, A243046, A243047 (positions of 0's), A360120 (their characteristic function).

Sequence in context: A028584 A243017 A084342 * A242931 A341828 A110645

Adjacent sequences: A243042 A243043 A243044 * A243046 A243047 A243048

Keyword

nonn,look

Author

Derek Orr, May 29 2014

Status

approved