A281528 - OEIS

A281528

a(n) = least numerator k such that the proper fraction k/n needs three or more terms as a signed sum of distinct unit fraction, or 0 if no such numerator exists.

0, 0, 0, 0, 0, 5, 0, 7, 0, 7, 0, 5, 10, 11, 11, 5, 13, 7, 13, 13, 14, 5, 17, 7, 10, 11, 17, 8, 19, 7, 13, 13, 10, 11, 23, 5, 11, 11, 17, 9, 25, 5, 17, 13, 10, 5, 29, 9, 14, 11, 19, 5, 22, 13, 17, 13, 11, 7, 37, 7, 13, 13, 19, 17, 26, 5, 20, 15, 22, 11, 29, 5, 10

(list; graph; refs; listen; history; text; internal format)

OFFSET

2,6

LINKS

Table of n, a(n) for n=2..74.

Index entries for sequences related to Egyptian fractions

PROG

(Magma) lst:=[]; for n in [2..74] do for k in [1..n-1] do f:=k/n; x:=1; v:=0; if Numerator(f) eq 1 then v:=1; else while f lt 2/x do if Numerator(Abs(f-1/x)) eq 1 then v:=1; break; end if; x+:=1; end while; end if; if v eq 0 then Append(~lst, k); break; end if; if k eq n-1 then Append(~lst, 0); end if; end for; end for; lst;

CROSSREFS

Cf. A281527.

Sequence in context: A062824 A292904 A271228 * A201334 A323643 A325966

Adjacent sequences: A281525 A281526 A281527 * A281529 A281530 A281531

KEYWORD

nonn

AUTHOR

Arkadiusz Wesolowski, Jan 23 2017

STATUS

approved