Creating Number Sequence without using Record ID#?

Hi Guys,
How to create a sequence of numbers without using Record ID#?


For Example

Record ID#        Sequence
1                           1            --> illustration 
2                           2
4                           3           --> Considering Record ID# = 3 is deleted.
5                           4







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Vivek Vishwanath
Hyderabad, India
+91 8185868789
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