cp's OEIS Frontend

A239233 Smaller member in a set of two distinct odd numbers the sum of whose reciprocals is 2/(2*n - 1), or 0 if no such integer exists.

%I A239233 #7 Mar 15 2014 05:40:35
%S A239233 0,0,3,0,5,0,7,9,9,0,11,0,13,15,15,0,17,21,19,21,21,0,23,0,25,27,27,
%T A239233 33,29,0,31,33,33,0,35,0,37,39,39,0,41,0,43,45,45,49,47,57,49,51,51,0,
%U A239233 53,0,55,57,57,69,59,63,61,63,63,0,65,0,67,69,69,0,71
%N A239233 Smaller member in a set of two distinct odd numbers the sum of whose reciprocals is 2/(2*n - 1), or 0 if no such integer exists.
%C A239233 a(n) = 0 if and only if n = 1 or 2*n - 1 is in A002145.
%e A239233 a(5) = 5 because 2/9 = 1/5 + 1/45.
%o A239233 (PARI) print1(0, ", "); forstep(n=3, 141, 2, f=2/n; y=0; if(!(isprime(n)&&Mod(n, 4)==3), y=2*floor((n+1)/4)+1; until(y==n, if(numerator(f-1/y)==1, break); y=y+2)); print1(y, ", "));
%Y A239233 Cf. A239036.
%K A239233 nonn
%O A239233 1,3
%A A239233 _Arkadiusz Wesolowski_, Mar 13 2014