

A120819


Indices of primes in A057137.


11




OFFSET

1,1


COMMENTS

Digits are in ascending order beginning with 1 and after 9 comes 0.
All terms must end in 1 or 7: A057137(n) is even when n is even, and divisible by 3 iff n == 0, 2, 3, 5, 6, 8 or 9 (mod 10).  M. F. Hasler, Apr 14 2024


REFERENCES

Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 61, 298.


LINKS



EXAMPLE

a(1) = 12345678901234567890...01234567890...012345678901 = A057137(171) is the first prime term in A057137.


MATHEMATICA

fQ[n_] := PrimeQ@ FromDigits@ Mod[Range@n, 10]; lst = {}; Do[ If[fQ@n, AppendTo[lst, n]; Print@n], {n, 10000}]; lst
IntegerLength[Select[Table[FromDigits[PadRight[{}, n, {1, 2, 3, 4, 5, 6, 7, 8, 9, 0}]], {n, 1, 1001, 2}], PrimeQ]] (* Harvey P. Dale, Feb 07 2024 *)


PROG

(PARI) N=0; for(n=1, 600, if(ispseudoprime(N=10*N+n%10), print1(n", "))) \\ Charles R Greathouse IV, May 10 2014 (Comment: Surprisingly, this is faster than calling ispseudoprime() only when n ends in 1 or 7, even when much larger N's are considered, e.g., up to 3000.  M. F. Hasler, Apr 14 2024)


CROSSREFS

Cf. A006055, A057137, A120828, A120820, A120821, A120822, A120823, A120824, A120825, A120826, A120827.


KEYWORD

base,hard,nonn,changed


AUTHOR



EXTENSIONS

18881 from Arjen K. Lenstra, Feb 20 2012


STATUS

approved



