A090517 Least k such that floor[(10^n)/k] is prime.

2, 9, 12, 13, 28, 19, 7, 27, 12, 13, 17, 74, 17, 14, 82, 66, 36, 44, 9, 36, 21, 13, 9, 90, 7, 19, 149, 51, 321, 35, 12, 14, 140, 13, 28, 42, 34, 36, 153, 155, 133, 46, 73, 106, 162, 109, 122, 42, 62, 422, 29, 231, 38, 34, 340, 295, 151, 197, 94, 19, 17, 83, 131, 66, 36

Offset

1,1

Links

Table of n, a(n) for n=1..65.

Example

a(1) = 2 as 10/2 = 5 is a prime. a(3) = 12 as floor[1000/12] = 83 is prime.

Mathematica

lkp[n_]:=Module[{k=2, c=10^n}, While[!PrimeQ[Floor[c/k]], k++]; k]; Array[ lkp, 70] (* Harvey P. Dale, Jul 09 2018 *)

Crossrefs

Cf. A090518, A090519, A090520.

Sequence in context: A083159 A041335 A042147 * A092191 A030376 A080520

Adjacent sequences: A090514 A090515 A090516 * A090518 A090519 A090520

Keyword

base,nonn

Author

Amarnath Murthy, Dec 07 2003

Extensions

Corrected and extended by Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Jan 28 2004

Further terms from David Wasserman, Dec 20 2005

Status

approved