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A077425
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a(n)= 1 (mod 4) (see A016813), but not a square (i.e. not in A000290).
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13
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5, 13, 17, 21, 29, 33, 37, 41, 45, 53, 57, 61, 65, 69, 73, 77, 85, 89, 93, 97, 101, 105, 109, 113, 117, 125, 129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 173, 177, 181, 185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 229, 233, 237, 241, 245, 249, 253, 257
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Pell equation x^2 - a(n)*y^2 = +4 has infinitely many (integer) solutions (see A077428 and A078355).
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LINKS
| S. R. Finch, Class number theory
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MAPLE
| issquare := proc(n::integer) local sq; sq := floor(sqrt(n)) ; if sq*sq = n then RETURN(true) ; else RETURN(false) ; fi ; end: A077425 := proc(n::integer) local resul, i ; resul := 5 ; i := 1 ; while i < n do resul := resul+4 ; while issquare(resul) do resul := resul+4 ; od ; i:= i+1 ; od ; RETURN(resul) ; end: for n from 1 to 31 do print(A077425(n)) ; od : - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 25 2006
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CROSSREFS
| Cf. A077426.
Sequence in context: A103666 A082700 A166409 * A039955 A014539 A074278
Adjacent sequences: A077422 A077423 A077424 * A077426 A077427 A077428
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KEYWORD
| nonn,easy
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AUTHOR
| Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de), Nov 29 2002
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EXTENSIONS
| More terms from Max Alekseyev (maxale(AT)gmail.com), Mar 03 2010
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