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A140515
Numbers n such that one of floor(10^n * Pi) or ceiling(10^n * Pi) is prime.
1
0, 1, 5, 11, 18, 37, 601, 1901, 2394, 3970, 5826, 16207
OFFSET
1,3
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
EXAMPLE
ceiling(10^11*Pi) = ceiling(314159265358.9...) = 314159265359 is prime, so 11 is in the sequence.
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 *)
PROG
(PARI) isA140515(n)=isprime(bitor(floor(10^n*Pi), 1))
CROSSREFS
Sequence in context: A140697 A048253 A102174 * A056996 A102184 A290751
KEYWORD
nonn,base,more
AUTHOR
Marvin Ray Burns, Jul 01 2008, Jul 02 2008
STATUS
approved