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A066755 Numbers n such that n^2 + 1 is not divisible by k^2 + 1 for any k in [1,n-1]. 1
1, 2, 4, 6, 10, 14, 16, 20, 24, 26, 34, 36, 40, 44, 46, 50, 54, 56, 60, 66, 70, 74, 76, 84, 86, 90, 94, 96, 100, 104, 110, 114, 116, 120, 124, 126, 130, 134, 136, 144, 146, 150, 156, 160, 164, 170, 176, 180, 184, 186, 190, 194, 196, 204, 206, 210, 214, 220, 224 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Equivalently, A066743(n)=1.

If n^2 + 1 is prime, n is in the sequence; i.e., the sequence contains A005574. But so are many other values of n: 34,44,46,50,60,70,76,86,96,...

LINKS

Harry J. Smith, Table of n, a(n) for n = 1..1000

MATHEMATICA

a66743[ n_ ] := Length[ Select[ Range[ 1, n ], IntegerQ[ (n^2+1)/(#^2+1) ]& ] ]; Select[ Range[ 1, 300 ], a66743[ # ]==1& ]

PROG

(PARI) { n=0; for (m=1, 10^10, k=1; b=1; t=m^2 + 1; while (k < m - 1, if (t%(k^2 + 1)==0, b=0; break); k++); if (b, write("b066755.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, Mar 23 2010

CROSSREFS

Cf. A066743, A005574.

Sequence in context: A213475 A075574 A104692 * A089238 A005574 A109807

Adjacent sequences:  A066752 A066753 A066754 * A066756 A066757 A066758

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Jan 16 2002

EXTENSIONS

Edited by Dean Hickerson, Jan 20 2002

STATUS

approved

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Last modified September 24 07:30 EDT 2018. Contains 315308 sequences. (Running on oeis4.)