def _eval(self, n, k):
# n.is_Number and k.is_Integer and k != 1 and n != k
if k.is_Integer:
if n.is_Integer and n >= 0:
n, k = int(n), int(k)
if k > n:
return S.Zero
elif k > n // 2:
k = n - k
if HAS_GMPY:
from sympy.core.compatibility import gmpy
return Integer(gmpy.bincoef(n, k))
d, result = n - k, 1
for i in range(1, k + 1):
d += 1
result = result * d // i
return Integer(result)
else:
d, result = n - k, 1
for i in range(1, k + 1):
d += 1
result *= d
result /= i
return result
def _eval(self, n, k):
# n.is_Number and k.is_Integer and k != 1 and n != k
from sympy.functions.elementary.exponential import log
from sympy.core import N
if k.is_Integer:
if n.is_Integer and n >= 0:
n, k = int(n), int(k)
if k > n:
return S.Zero
elif k > n // 2:
k = n - k
if HAS_GMPY:
from sympy.core.compatibility import gmpy
return Integer(gmpy.bincoef(n, k))
d, result = n - k, 1
for i in range(1, k + 1):
d += 1
result = result * d // i
return Integer(result)
else:
d, result = n - k, 1
for i in range(1, k + 1):
d += 1
result *= d
result /= i
return result
def _eval(self, n, k):
# n.is_Number and k.is_Integer and k != 1 and n != k
from sympy.functions.elementary.exponential import log
from sympy.core import N
if k.is_Integer:
if n.is_Integer and n >= 0:
n, k = int(n), int(k)
if k > n:
return S.Zero
elif k > n // 2:
k = n - k
if HAS_GMPY:
from sympy.core.compatibility import gmpy
return Integer(gmpy.bincoef(n, k))
prime_count_estimate = N(n / log(n))
# if the number of primes less than n is less than k, use prime sieve method
# otherwise it is more memory efficient to compute factorials explicitly
if prime_count_estimate < k:
M, result = int(_sqrt(n)), 1
for prime in sieve.primerange(2, n + 1):
if prime > n - k:
result *= prime
elif prime > n // 2:
continue
elif prime > M:
if n % prime < k % prime:
result *= prime
else:
N, K = n, k
exp = a = 0
while N > 0:
a = int((N % prime) < (K % prime + a))
N, K = N // prime, K // prime
exp = a + exp
if exp > 0:
result *= prime**exp
else:
result = ff(n, k) / factorial(k)
return Integer(result)
else:
d = result = n - k + 1
for i in range(2, k + 1):
d += 1
result *= d
result /= i
return result
def _eval(self, n, k):
# n.is_Number and k.is_Integer and k != 1 and n != k
from sympy.functions.elementary.exponential import log
from sympy.core import N
if k.is_Integer:
if n.is_Integer and n >= 0:
n, k = int(n), int(k)
if k > n:
return S.Zero
elif k > n // 2:
k = n - k
if HAS_GMPY:
from sympy.core.compatibility import gmpy
return Integer(gmpy.bincoef(n, k))
prime_count_estimate = N(n / log(n))
# if the number of primes less than n is less than k, use prime sieve method
# otherwise it is more memory efficient to compute factorials explicitly
if prime_count_estimate < k:
M, result = int(_sqrt(n)), 1
for prime in sieve.primerange(2, n + 1):
if prime > n - k:
result *= prime
elif prime > n // 2:
continue
elif prime > M:
if n % prime < k % prime:
result *= prime
else:
N, K = n, k
exp = a = 0
while N > 0:
a = int((N % prime) < (K % prime + a))
N, K = N // prime, K // prime
exp = a + exp
if exp > 0:
result *= prime**exp
else:
result = ff(n, k) / factorial(k)
return Integer(result)
else:
d = result = n - k + 1
for i in range(2, k + 1):
d += 1
result *= d
result /= i
return result
def _eval(self, n, k):
# n.is_Number and k.is_Integer and k != 1 and n != k
if k.is_Integer:
if n.is_Integer and n >= 0:
n, k = int(n), int(k)
if k > n:
return S.Zero
elif k > n // 2:
k = n - k
if HAS_GMPY:
from sympy.core.compatibility import gmpy
return Integer(gmpy.bincoef(n, k))
M, result = int(_sqrt(n)), 1
for prime in sieve.primerange(2, n + 1):
if prime > n - k:
result *= prime
elif prime > n // 2:
continue
elif prime > M:
if n % prime < k % prime:
result *= prime
else:
N, K = n, k
exp = a = 0
while N > 0:
a = int((N % prime) < (K % prime + a))
N, K = N // prime, K // prime
exp = a + exp
if exp > 0:
result *= prime**exp
return Integer(result)
else:
d = result = n - k + 1
for i in range(2, k + 1):
d += 1
result *= d
result /= i
return result
