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A184775 Numbers k such that floor(k*sqrt(2)) is prime. 6
2, 4, 5, 8, 14, 21, 22, 29, 31, 38, 42, 48, 52, 56, 59, 63, 69, 72, 73, 76, 80, 90, 93, 97, 106, 107, 123, 127, 128, 137, 140, 141, 158, 161, 162, 165, 169, 171, 178, 182, 186, 192, 196, 199, 220, 222, 239, 246, 247, 250, 254, 260, 264, 268, 271, 281, 284, 298, 305, 311, 318 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

EXAMPLE

See A184774.

MATHEMATICA

r=2^(1/2); s=r/(r-1);

a[n_]:=Floor [n*r];  (* A001951 *)

b[n_]:=Floor [n*s];  (* A001952 *)

Table[a[n], {n, 1, 120}]

t1={}; Do[If[PrimeQ[a[n]], AppendTo[t1, a[n]]], {n, 1, 600}]; t1

t2={}; Do[If[PrimeQ[a[n]], AppendTo[t2, n]], {n, 1, 600}]; t2

t3={}; Do[If[MemberQ[t1, Prime[n]], AppendTo[t3, n]], {n, 1, 300}]; t3

t4={}; Do[If[PrimeQ[b[n]], AppendTo[t4, b[n]]], {n, 1, 600}]; t4

t5={}; Do[If[PrimeQ[b[n]], AppendTo[t5, n]], {n, 1, 600}]; t5

t6={}; Do[If[MemberQ[t4, Prime[n]], AppendTo[t6, n]], {n, 1, 300}]; t6

(* the lists t1, t2, t3, t4, t5, t6 match the sequences

A184774, A184775, A184776 , A184777, A184778, A184779 *)

PROG

(PARI) isok(n) = isprime(floor(n*sqrt(2))); \\ Michel Marcus, Apr 10 2018

CROSSREFS

Cf. A001951, A184774, A184776.

Sequence in context: A278695 A105134 A226791 * A240075 A272229 A229083

Adjacent sequences:  A184772 A184773 A184774 * A184776 A184777 A184778

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 21 2011

STATUS

approved

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Last modified May 5 18:20 EDT 2021. Contains 343572 sequences. (Running on oeis4.)