A061195 Minimum positive numerator of s_1/1 + ... + s_n/n in lowest terms, where each s_i equals 1 or -1.
1, 1, 1, 1, 7, 1, 11, 9, 11, 11, 23, 23, 607, 251, 59, 25, 97, 97, 2647, 2647, 1337, 457, 8917, 8917, 7951, 4261, 12439, 12439, 587971, 587971, 9687661, 13828799, 505163, 1554793, 1554793, 1554793, 1526171
Offset: 1
Keywords
Examples
1/1 - 1/2 - 1/3 + 1/4 - 1/5 - 1/6 = 1/20, so a(6)=1.
Programs
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Mathematica
nMax = 19; d = {0}; Table[d = Flatten[{d + 1/n, d - 1/n}]; Min[Abs[Numerator[d]]], {n, nMax}] (* T. D. Noe, Nov 19 2013 *) -
PARI
a(n) = {lcmn = 1;for (i=1, n, lcmn = lcm(i, lcmn)); minn = lcmn; for (i=0, 2^(n-1)-1, b = binary(i); while (#b != n, b = concat(0, b);); num = numerator(abs(sum(ii = 1, n, (-1)^b[ii]/ii))); minn = min(minn, num);); return(minn);} \\ Michel Marcus, Jun 15 2013
Extensions
More terms from Naohiro Nomoto, Jun 24 2001
a(22)-a(25) from Zak Seidov, Nov 20 2013
a(26)-a(33) from Zak Seidov, Nov 24 2013
a(34)-a(37) from Giovanni Resta, Jun 12 2016