OFFSET
0,2
LINKS
Chai Wah Wu, Table of n, a(n) for n = 0..715
FORMULA
EXAMPLE
PROG
(PARI) a(n)=A020639(4^(2*n+1)\5+1). \\ Using factor(...)[1, 1] requires complete factorization and is much less efficient for large n.
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, Feb 22 2018
STATUS
approved