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A285804 Composite numbers of the form 12*k+5 or 12*k+7 for some k. 0
55, 65, 77, 91, 115, 125, 161, 175, 185, 187, 209, 221, 235, 245, 247, 259, 295, 305, 319, 329, 341, 343, 355, 365, 377, 391, 403, 413, 415, 425, 427, 437, 451, 473, 475, 485, 497, 511, 533, 535, 545, 559, 581, 583, 595, 605, 629, 655, 665 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: Let r(n) = (a(n)-1)/(a(n)+1)) if a(n) mod 4 = 1, (a(n)+1)/(a(n)-1)) otherwise; then Product_{n>=1} r(n) = (28/27) * (32/33) * (38/39) * (46/45) * ... = 1.

LINKS

Table of n, a(n) for n=1..49.

MAPLE

remove(isprime, [seq(seq(12*k+j, j=[5, 7]), k=1..100)]); # Robert Israel, Apr 28 2017

PROG

(PARI) {

for(n=0, 100,

    n12=12*n; n5=n12+5; n7=n12+7;

    if(!isprime(n5), print1(n5", "));

    if(!isprime(n7), print1(n7", "))

   )

}

CROSSREFS

Sequence in context: A039356 A043179 A043959 * A269808 A004434 A168109

Adjacent sequences:  A285801 A285802 A285803 * A285805 A285806 A285807

KEYWORD

nonn

AUTHOR

Dimitris Valianatos, Apr 26 2017

STATUS

approved

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Last modified November 11 15:59 EST 2019. Contains 329019 sequences. (Running on oeis4.)