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A004614
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Numbers that are divisible only by primes congruent to 3 mod 4.
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9
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1, 3, 7, 9, 11, 19, 21, 23, 27, 31, 33, 43, 47, 49, 57, 59, 63, 67, 69, 71, 77, 79, 81, 83, 93, 99, 103, 107, 121, 127, 129, 131, 133, 139, 141, 147, 151, 161, 163, 167, 171, 177, 179, 189, 191, 199, 201, 207, 209, 211, 213, 217, 223, 227, 231, 237, 239, 243, 249, 251
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Numbers whose factorization as Gaussian integers is the same as their factorization as integers. - Frank Adams-Watters (FrankTAW(AT)Netscape.net), Oct 14 2005
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..10000
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MATHEMATICA
| ok[1] = True; ok[n_] := And @@ (Mod[#, 4] == 3 &) /@ FactorInteger[n][[All, 1]]; Select[Range[251], ok] (* From Jean-François Alcover, May 05 2011 *)
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PROG
| (PARI) for(n=1, 1000, if(sumdiv(n, d, isprime(d)*if((d-3)%4, 1, 0))==0, print1(n, ", ")))
(PARI) forstep(n=1, 999, 2, for(j=1, #t=factor(n)[, 1], t[j]%4==1&next(2)); print1(n", ")) - M. F. Hasler (www.univ-ag.fr/~mhasler), Feb 26 2008
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CROSSREFS
| Cf. A004613.
Sequence in context: A156770 A088630 A129747 * A112398 A197504 A167800
Adjacent sequences: A004611 A004612 A004613 * A004615 A004616 A004617
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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