OFFSET
1,3
EXAMPLE
For n=3, prime(prime(3)-1) = 7, and prime(3) = 5, therefore a(3) = 7 - 5 = 2.
MATHEMATICA
Table[Prime[Prime[n]-1] - Prime[n], {n, 1, 100}]
PROG
(PARI) a(n) = prime(prime(n)-1) - prime(n); \\ Michel Marcus, Aug 18 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Terry D. Grant, Aug 15 2016
STATUS
approved