A061999 a(n) = 2*a(n-1)^2 - 2*a(n-2)^2 with a(0) = 0, a(1) = 1.
0, 1, 2, 6, 64, 8120, 131860608, 34774439752390528, 2418523320185277177863741363978240, 11698510100560033501377640350194228137500049288930688305497138757632
Offset: 0
Keywords
Links
- Harry J. Smith, Table of n, a(n) for n = 0..12
Crossrefs
Cf. A062000.
Programs
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Mathematica
Join[{a=0,b=1},Table[c=2*b^2-2*a^2;a=b;b=c,{n,10}]] (* Vladimir Joseph Stephan Orlovsky, Jan 22 2011 *) nxt[{a_,b_}]:={b,2b^2-2a^2}; NestList[nxt,{0,1},10][[All,1]] (* Harvey P. Dale, Apr 05 2022 *) -
PARI
{ for (n=0, 12, if (n>1, a=2*a1^2-2*a2^2; a2=a1; a1=a, if (n==0, a=a2=0, a=a1=1)); write("b061999.txt", n, " ", a) ) } \\ Harry J. Smith, Jul 29 2009 -
SageMath
def a(n): # a = A061999 if (n<2): return n else: return 2*(a(n-1)^2 - a(n-2)^2) [a(n) for n in (0..14)] # G. C. Greubel, May 01 2022
Formula
a(n) = A062000(n)/2.