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A184778
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Numbers k such that 2k + floor(k*sqrt(2)) is prime.
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7
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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
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OFFSET
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1,2
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LINKS
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EXAMPLE
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MATHEMATICA
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r=2^(1/2); s=r/(r-1);
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
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PROG
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(Python)
from itertools import count, islice
from math import isqrt
from sympy import isprime
def A184778_gen(): # generator of terms
return filter(lambda k:isprime((k<<1)+isqrt(k**2<<1)), count(1))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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