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A072901 Composite numbers n such that the discriminant of the quadratic field Q(sqrt(n)) equals 4n. 0
6, 10, 14, 15, 22, 26, 30, 34, 35, 38, 39, 42, 46, 51, 55, 58, 62, 66, 70, 74, 78, 82, 86, 87, 91, 94, 95, 102, 106, 110, 111, 114, 115, 118, 119, 122, 123, 130, 134, 138, 142, 143, 146, 154, 155, 158, 159, 166, 170, 174, 178, 182, 183, 186, 187, 190, 194, 195 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: All terms are squarefree. Example: 6=2*3; 15=3*5; 30=2*3*5; 154=2*7*11; 195=3*5*13. - Vincenzo Librandi, Aug 08 2010 and Michel Marcus, Nov 26 2013

If prime numbers were accepted, then sequence A230375 would have been obtained. - Michel Marcus, Nov 26 2013

LINKS

Table of n, a(n) for n=1..58.

Wikipedia, Quadratic field

PROG

(PARI) isok(n) = !isprime(n) && (quaddisc(n) == 4*n); \\ Michel Marcus, Nov 26 2013

CROSSREFS

Cf. A037449.

Sequence in context: A063078 A064452 A085647 * A162409 A226494 A242920

Adjacent sequences:  A072898 A072899 A072900 * A072902 A072903 A072904

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Aug 10 2002

STATUS

approved

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Last modified September 25 13:01 EDT 2020. Contains 337344 sequences. (Running on oeis4.)