<Li> The first check digit is calculated through an algorithm involving modulo 11 of weighted sum of the nine first digits . </Li> <Dl> <Dd> The second check digit is calculated through a similar algorithm involving the 10 first digits . </Dd> </Dl> <Dd> The second check digit is calculated through a similar algorithm involving the 10 first digits . </Dd> <Ul> <Li> People who do not permanently reside in Norway have been assigned a D - number upon registration in the population register . The D - number is like a birth number, but with the day of the month increased by 40 . D comes from the Norwegian name of an authority for sailors, which previously issued those numbers, usually to sailors on board Norwegian ships . Nowadays foreign seasonal workers, for example in the tourist industry, get D - numbers . </Li> </Ul>

When was the first social security numbers issued