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

1,3

Comments

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

Links

Table of n, a(n) for n=1..71.

Example

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

Prog

(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, ", "));

Crossrefs

Cf. A239036.

Sequence in context: A353154 A325962 A210451 * A051704 A049689 A227901

Adjacent sequences: A239230 A239231 A239232 * A239234 A239235 A239236

Keyword

nonn

Author

Arkadiusz Wesolowski, Mar 13 2014

Status

approved