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A091113
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Nonprimes of the form 4*k+1.
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16
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1, 9, 21, 25, 33, 45, 49, 57, 65, 69, 77, 81, 85, 93, 105, 117, 121, 125, 129, 133, 141, 145, 153, 161, 165, 169, 177, 185, 189, 201, 205, 209, 213, 217, 221, 225, 237, 245, 249, 253, 261, 265, 273, 285, 289, 297, 301, 305, 309, 321, 325, 329, 333, 341, 345
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OFFSET
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1,2
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LINKS
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MAPLE
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option remember;
if n =1 then
1;
else
for a from procname(n-1)+4 by 4 do
if not isprime(a) then
return a;
end if;
end do:
end if;
end proc:
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MATHEMATICA
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Do[If[ !PrimeQ[n]&&Equal[Mod[n, 4], 1], Print[n]], {n, 1, 1000}]
Select[4*Range[0, 100]+1, !PrimeQ[#]&] (* Harvey P. Dale, Oct 28 2017 *)
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PROG
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(GAP) Filtered(List([0..100], k->4*k+1), n->not IsPrime(n)); # Muniru A Asiru, Mar 10 2019
(Magma) [n: n in [1..350] | IsIntegral((n-1)/4) and not IsPrime(n)]; // G. C. Greubel, Mar 10 2019
(Sage) [n for n in (1..350) if ((n-1)/4).is_integer() and not is_prime(n)] # G. C. Greubel, Mar 10 2019
(PARI) isok(n) = !isprime(n) && !((n-1) % 4); \\ Michel Marcus, Mar 11 2019
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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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