def _is_safe_size(n):
n = int(n)<EOL>if n == <NUM_LIT:0>:<EOL><INDENT>return True<EOL><DEDENT>for c in (<NUM_LIT:3>, <NUM_LIT:5>):<EOL><INDENT>while n % c == <NUM_LIT:0>:<EOL><INDENT>n //= c<EOL><DEDENT><DEDENT>return not n & (n-<NUM_LIT:1>)<EOL>
Is the size of FFT such that FFTPACK can handle it in single precision
with sufficient accuracy?

Composite numbers of 2, 3, and 5 are accepted, as FFTPACK has those