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A134660
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Number of odd coefficients in (1 + x + x^2 + x^3)^n.
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5
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1, 4, 4, 4, 4, 16, 4, 8, 4, 16, 16, 4, 4, 16, 8, 16, 4, 16, 16, 16, 16, 64, 4, 8, 4, 16, 16, 8, 8, 32, 16, 32, 4, 16, 16, 16, 16, 64, 16, 32, 16, 64, 64, 4, 4, 16, 8, 16, 4, 16, 16, 16, 16, 64, 8, 16, 8, 32, 32, 16, 16, 64, 32, 64, 4, 16, 16, 16, 16, 64, 16, 32, 16, 64, 64, 16, 16, 64
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OFFSET
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0,2
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LINKS
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FORMULA
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EXAMPLE
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Written as an irregular triangle in which the row lengths are the terms of A011782, the sequence begins:
1;
4;
4,4;
4,16,4,8;
4,16,16,4,4,16,8,16;
4,16,16,16,16,64,4,8,4,16,16,8,8,32,16,32;
4,16,16,16,16,64,16,32,16,64,64,4,4,16,8,16,4,16,16,16,16,64,8,16,8,32,32,16,16,64,32,64;
...
(End)
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MAPLE
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seq(igcd(4^n, binomial(4*n, n)), n=0..77); # Peter Luschny, Nov 08 2011
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MATHEMATICA
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PolynomialMod[(1+x+x^2+x^3)^n, 2] /. x->1
A036555 = Total /@ IntegerDigits[3 Range[0, 100], 2]; Table[2^A036555[[n]], {n, 1, 20}] (* or *) Table[GCD[4^n, Binomial[4*n, n]], {n, 0, 50}] (* G. C. Greubel, Dec 31 2017 *)
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PROG
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(PARI) a(n) = {my(pol= Pol([1, 1, 1, 1], xx)*Mod(1, 2)); subst(lift(pol^n), xx, 1); } \\ Michel Marcus, Mar 01 2015
(PARI) a(n) = 2^hammingweight(3*n); \\ Joerg Arndt, Mar 10 2015
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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