OFFSET
0,2
COMMENTS
LINKS
Indranil Ghosh (terms 0..1000) & Antti Karttunen, Table of n, a(n) for n = 0..8191
PROG
(Scheme) (define (A209636 n) (let loop ((n (* 2 n)) (m 1)) (cond ((< n 2) m) ((even? n) (loop (/ n 2) (* m 2))) (else (loop (/ (- n 1) 2) (A000040 m))))))
(PARI) A209636(n) = { my(n=2*n, m=1); while(n >= 2, if(!(n%2), m*=2, m = prime(m)); n\=2); m; } \\ Antti Karttunen, May 25 2017
(Python)
from sympy import prime
def a(n):
n = 2*n
m = 1
if n<2: return 1
while n>1:
if n%2==0:
n//=2
m*=2
else:
n=(n - 1)//2
m=prime(m)
return m
print([a(n) for n in range(101)]) # Indranil Ghosh, May 25 2017, translated from Antti Karttunen's SCHEME code
CROSSREFS
KEYWORD
AUTHOR
Antti Karttunen, Mar 11 2012
STATUS
approved