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A203812 Numbers n where abs(s(n)) produces a new minimum, with s(1) = 1 and s(i) = s(i-1) - sign(s(i-1))*(1/i). 4
1, 2, 3, 4, 6, 8, 10, 12, 14, 16, 18, 22, 30, 38, 54, 70, 118, 126, 134, 150, 166, 182, 198, 214, 246, 278, 374, 534, 598, 662, 790, 854, 982, 1110, 1238, 1366, 1494, 1622, 1878, 2006, 2134, 2390, 2902, 3158, 3670, 5462, 5974, 6486, 6998, 10070, 11094, 12118 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Positions of decreasing minima of abs(A203810(i)/A203811(i)).

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 1..100

EXAMPLE

The first 4 fractions f(i)=A203810(i)/A203811(i) 1/1, 1/2, 1/6, -1/12 have decreasing absolute values. Therefore a(1)=1, a(2)=2, a(3)=3, a(4)=4. 5 is not in the sequence, because f(5)=7/60>1/12, but f(6)=-1/20 gives a(5)=6 because 1/20<1/12.

Fractions producing further decreasing absolute values are f(8)=-9/280, f(10)=-53/2520, f(12)=-373/27720, f(14)=-2869/360360, f(16)=-547/144144, f(18)=-1291/2450448, f(22)=-13913/232792560, f(30)=93259013/232908956280.

PROG

(PARI)

s=0; d=2; \

for (k=1, 12500, if(s>0, s-=1/k, s+=1/k); if(abs(s)<d, d=abs(s); print1(k, ", ")))

\\ Hugo Pfoertner, Nov 14 2017

CROSSREFS

Cf. A203810, A203811.

Sequence in context: A064376 A283808 A068578 * A047894 A113769 A056865

Adjacent sequences:  A203809 A203810 A203811 * A203813 A203814 A203815

KEYWORD

nonn

AUTHOR

Hugo Pfoertner and Rainer Rosenthal, Jan 06 2012

STATUS

approved

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Last modified September 15 16:40 EDT 2019. Contains 327078 sequences. (Running on oeis4.)