A140515 Numbers n such that one of floor(10^n * Pi) or ceiling(10^n * Pi) is prime.

0, 1, 5, 11, 18, 37, 601, 1901, 2394, 3970, 5826, 16207

Offset: 1

Author

Marvin Ray Burns, Jul 01 2008, Jul 02 2008

Keywords

• nonn
• base
• more

Examples

			ceiling(10^11*Pi) = ceiling(314159265358.9...) = 314159265359 is prime, so 11 is in the sequence.
		

Links

• Carlos B. Rivera F. Puzzle 50. Approximation to pi with primes, The Prime Puzzles and Problems Connection.
• Eric Weisstein's World of Mathematics, Pi Digits

Programs

Mathematica

npQ[n_]:=Module[{c=10^n Pi},Total[Boole[PrimeQ[{Floor[ c],Ceiling[ c]}]]] == 1]; Select[Range[0,4000],npQ] (* The program generates the first 10 terms of the sequence. To generate more, increase the Range constant, but the program may take a long time to run. *) (* Harvey P. Dale, May 07 2021 *)

PARI

isA140515(n)=isprime(bitor(floor(10^n*Pi),1))