OFFSET
1,1
COMMENTS
Single-digit numbers 0, ..., 9 seem to be excluded but would satisfy the condition voidly. - M. F. Hasler, May 10 2018
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
EXAMPLE
998471 is in the sequence because all the five numbers 9098471, 9908471, 9980471, 9984071 and 9984701 are primes.
MATHEMATICA
f[n_]:=(r=IntegerDigits[n]; l=Length[r]; For[k=2, PrimeQ[FromDigits[Insert
[r, 0, k]]], k++ ]; If[k==l+1, n, 0]); Select[Range[11, 560], f[ # ]>0&]
PROG
(PARI) is(n, L=logint(n+!n, 10)+1, P)={!for(k=1, L-1, isprime([10*P=10^(L-k), 1]*divrem(n, P))||return) && n>9} \\ M. F. Hasler, May 10 2018
CROSSREFS
Cf. A216169 (subset of composite terms), A215417 (subset of primes), A159236 (0 is inserted between all digits).
Cf. A068679 (1 is prefixed, appended or inserted anywhere), A069246 (primes among these), A068673 (1 is prefixed, or appended).
Cf. A069832 (7 is prefixed, appended or inserted anywhere), A215420 (primes among these), A068677 (7 is prefixed or appended).
Cf. A158232 (13 is prefixed or appended).
KEYWORD
base,easy,nonn
AUTHOR
Farideh Firoozbakht, Sep 22 2009
EXTENSIONS
Erroneous comment and cross-references deleted by M. F. Hasler, May 10 2018
STATUS
approved