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.

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, 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, 53, 0, 55, 57, 57, 69, 59, 63, 61, 63, 63, 0, 65, 0, 67, 69, 69, 0, 71

Offset: 1

Author

Arkadiusz Wesolowski, Mar 13 2014

Keywords

• nonn

Comments

a(n) = 0 if and only if n = 1 or 2*n - 1 is in A002145.

Examples

			a(5) = 5 because 2/9 = 1/5 + 1/45.
		

Crossrefs

Cf. A239036.

Programs

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, ", "));