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A184778 Numbers k such that 2k + floor(k*sqrt(2)) is prime. 7
1, 4, 5, 7, 11, 14, 18, 21, 32, 41, 46, 48, 49, 56, 62, 79, 83, 86, 90, 93, 97, 114, 120, 123, 127, 130, 134, 137, 144, 165, 169, 172, 178, 181, 185, 188, 213, 220, 222, 223, 237, 243, 246, 250, 253, 257, 260, 267, 288, 302, 308, 311, 325, 329, 343, 346, 352, 360, 366, 369, 376 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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) is(n)=isprime(sqrtint(2*n^2)+2*n) \\ Charles R Greathouse IV, May 22 2017

CROSSREFS

Cf. A184774, A184777, A184779.

Sequence in context: A175903 A080327 A283485 * A240118 A343211 A237133

Adjacent sequences:  A184775 A184776 A184777 * A184779 A184780 A184781

KEYWORD

nonn

AUTHOR

Clark Kimberling, Jan 21 2011

STATUS

approved

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Last modified May 9 03:39 EDT 2021. Contains 343685 sequences. (Running on oeis4.)