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A004795
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Least positive unitary linear combination of distinct numbers in row n of Pascal's triangle; i.e., least positive sum of form d(0)C(n-1,0) + d(1)C(n-1,1) + ...+ d(m)C(n-1,m), d(i)=+-1, m = floor((n+1)/2).
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0
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1, 1, 1, 2, 1, 4, 2, 6, 5, 2, 22, 10, 64, 64, 102, 126, 33, 220, 1902, 132, 2202, 604, 2120, 942, 22768, 4044, 234638, 7436, 614482, 8264, 107008, 23776, 11154697, 4336, 1152138, 129812, 37815814, 245272, 23068832, 341506, 12223534, 427260, 53970758
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OFFSET
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1,4
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LINKS
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PROG
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(PARI) padbin(n, len) = my(b = binary(n)); while(length(b) < len, b = concat(0, b); ); b;
a(n) = m = (n+1)\2; nb = 2^(m+1); lps = 0; v = vector(m, i, binomial(n-1, i-1)); for (i = 1, nb-1, vb = padbin(i, m+1); s = sum(k = 1, m, if (vb[k], v[k], -v[k])); if ((s>0), if (lps == 0, lps = s, if (s < lps, lps = s; ); )); ); lps; \\ Michel Marcus, Sep 30 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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