OFFSET
1,1
COMMENTS
More formally: positive numbers with decimal expansion (d_1, ..., d_w) (where d_1 <> 0) such that for any i in 1..w, we have some j, k such that j <= i <= k and d_j <> 0 and (d_j, ..., d_k) corresponds to the decimal expansion of a prime number.
EXAMPLE
The number 15195 belongs to the sequence for the following covering:
151
19
5
.....
15195
PROG
(PARI) is(n, base = 10) = { my (d = if (n, digits(n, base), [0]), ok = vector(#d), rem = #d); for (i = 1, #d, if (d[i], for (j = i, #d, if (isprime( fromdigits( d[i..j], base)), for (k = i, j, if (ok[k]==0, ok[k]++; rem--; if (rem==0, return (1)))))))); return (0); }
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Rémy Sigrist, Jan 20 2024
STATUS
approved