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A260551
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Number of polynomials P = Sum_{k=0..m} x^{d(k)} with 0 = d(0) < ... < d(m) and P^2 = Sum_{k>=0} B(k) x^k such that B(k) <= n for all k and B(k) > 0 for k <= d(m).
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3
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OFFSET
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1,2
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LINKS
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EXAMPLE
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For n=1, the only possible polynomial is P = 1 (the coefficient of x^0 must always be 1), and its square P^2 = 1 satisfies the conditions. If another term is added, there will be a coefficient 2 > n in the square, which is forbidden.
For n=2, the 3 polynomials are {1, x+1, x^3+x+1}. P = x^2+1 is excluded because P^2 has a zero coefficient for x^1. P = x^2+x+1 is excluded because P^2 has a coefficient 3 > n which is forbidden. If the degree is > 3, then either there will be a zero coefficient in P^2 below deg(P), or there will be a coefficient > 2.
For n=3, the 9 polynomials are {1, x+1, x^2+x+1, x^3+x+1, x^4+x^2+x+1, x^5+x^2+x+1, x^5+x^3+x+1, x^7+x^4+x^2+x+1, x^8+x^5+x^2+x+1}.
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PROG
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(PARI) A260551(n, c=1, L=2<<[1, 3, 8, 40, 52, 264, 328][n])={c||c=[1]; forstep(i=2, L, 2, normlp(P2=Pol(binary(1+i))^2)>n&&next; for(k=1, #binary(i), component(P2, k)||next(2)); if(type(c)!="t_INT", c=concat(c, Pol(binary(1+i))), c++)); c} \\ Use 2nd arg=0 or [] to get the list of polynomials. For n>3 this code takes too long, but you may give a lower limit as 3rd arg to get quickly a list of the first 200-300 solutions. - M. F. Hasler, Jul 31 2015
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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Definition and examples clarified by M. F. Hasler, Jul 31 2015
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STATUS
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approved
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