OFFSET
1,2
COMMENTS
For odd primes p, Charles Babbage showed in 1819 that a(p) = 1.
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000
EXAMPLE
a(11) = binomial(21,10) mod 11^2 = 352716 mod 121 = 1.
MATHEMATICA
Table[ Mod[ Binomial[2n - 1, n - 1], n^2], {n, 60}] (* Robert G. Wilson v, Dec 14 2004 *)
PROG
(Magma) [Binomial(2*n-1, n-1) mod(n^2): n in [1..65]]; // Vincenzo Librandi, Jul 29 2015
(PARI) A099906(n)=binomial(2*n-1, n-1)%n^2 \\ M. F. Hasler, Jul 30 2015
(Python)
from __future__ import division
A099906_list, b = [], 1
for n in range(1, 10001):
A099906_list.append(b % n**2)
b = b*2*(2*n+1)//(n+1) # Chai Wah Wu, Jan 26 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Oct 29 2004
STATUS
approved