A073077 Numbers k that divide C(2k,k) and C(4k,2k).

1, 2, 20, 110, 156, 210, 220, 238, 240, 312, 460, 468, 483, 510, 561, 600, 624, 665, 684, 696, 720, 744, 770, 806, 812, 816, 868, 936, 966, 1001, 1012, 1045, 1064, 1100, 1110, 1122, 1144, 1155, 1170, 1200, 1295, 1309, 1320, 1326, 1332, 1360, 1368, 1394, 1404

Offset: 1

Author

Benoit Cloitre, Aug 17 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A014847.

Cf. A000984, A001448.

Programs

Mathematica

Select[Range[1500], Divisible[Binomial[2*#, #], #] && Divisible[Binomial[4*#, 2*#], #] &] (* Amiram Eldar, Apr 26 2025 *)

PARI

isok(n) = !(binomial(2*n, n) % n) && !(binomial(4*n, 2*n) % n); \\ Michel Marcus, Nov 28 2013

Extensions

More terms from Michel Marcus, Nov 28 2013