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A099202
a(n) = 2^floor(n^2/2).
2
1, 1, 4, 16, 256, 4096, 262144, 16777216, 4294967296, 1099511627776, 1125899906842624, 1152921504606846976, 4722366482869645213696, 19342813113834066795298816, 316912650057057350374175801344
OFFSET
0,3
COMMENTS
Hankel transform of A168490. Linked to elliptic curve y^2=1-12x+44x^2-48x^3 through g.f. of A168490.- Paul Barry, Nov 27 2009
LINKS
FORMULA
a(n) = A016116(n) * A006125(n)
a(n) = 16a(n-2)^2 / a(n-4). - Michael Somos, Sep 16 2005
a(n) = 4^floor(n^2/4) = 4^A002620(n). - Paul Barry, Nov 27 2009
PROG
(PARI) a(n)=2^(n^2\2)
(Magma) [2^Floor(n^2/2): n in [0..20]]; // Vincenzo Librandi, Aug 16 2011
(Python)
def A099202(n): return 1<<(n**2>>1) # Chai Wah Wu, Jan 18 2023
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Oct 04 2004
STATUS
approved