OFFSET
1,2
EXAMPLE
We have a(10) = 9 since all primes up to the 10th (2, 3, 5, 7, 11, 13, 17, 19, 23, 29) use the 9 prime digits 2, 3, 5, 7, 3, 7, 2, 3, 2.
MATHEMATICA
With[{s = IntegerDigits[Prime@ Range@ 64]}, Array[Count[Flatten[s[[1 ;; #]] ], _?PrimeQ] &, Length@ s]] (* Michael De Vlieger, Mar 27 2019 *)
PROG
(PARI) a(n) = sum(k=1, prime(n), if (isprime(k), #select(x->isprime(x), digits(k)))); \\ Michel Marcus, Mar 23 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Lekraj Beedassy, Mar 15 2019
STATUS
approved