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 A233794 A bit array representing the primes between 105n-102 and 105n+2 among those numbers in the range relatively prime to 6. 1

%I #17 Jan 20 2015 06:04:01

%S 32596917119,19221276355,32294916984,27056746064,13260585324,

%T 19153906256,11044217692,10628959443,23930632312,27274595010,

%U 12929300524,9758853778,21477751664,18735703058,6820532604,1946775235,27961930040,10687629457,28253630548,10613958227

%N A bit array representing the primes between 105n-102 and 105n+2 among those numbers in the range relatively prime to 6.

%C From Riesel: "In a 36-bit computer, the primes in an interval from 105k to 105(k+1) can thus be stored in 35 of the 36 bits of a computer word. This string of bits may be reversed and printed out as an integer <2^35. A prime table up to 105 × 100 = 10500 looks rather strange when printed out in this way (see next page) [this sequence]. The reader should compare this with the prime table up to 12553 provided at the end of this book. The table printed there contains slightly more information than the print-out on the next page, .... On a 3.5 inch magneto-optical disk, having a storage capacity of 128 Mbytes, there is enough room to store the primes up to about 3,000,000,000 in this way."

%C a(n) = 0 for almost all n. The first such n is 19151. - _Charles R Greathouse IV_, Dec 22 2013

%D Hans Riesel, Prime Numbers and Computer Methods for Factorization, Second Edition, Birkhäuser, Boston, 1994, pp 8-10.

%H T. D. Noe, <a href="/A233794/b233794.txt">Table of n, a(n) for n = 1..10000</a>

%t Table[t = Select[Range[105*(n - 1) + 3, 105*n + 2], ! IntegerQ[#/2] && ! IntegerQ[#/3] &]; FromDigits[Reverse[Table[If[PrimeQ[i], 1, 0], {i, t}]], 2], {n, 20}] (* _T. D. Noe_, Dec 30 2013 *)

%o (PARI) a(n)=my(s);forstep(n=105*n+2,105*n-102,-1, if(gcd(n,6)>1,next); s+=s+isprime(n));s \\ _Charles R Greathouse IV_, Dec 22 2013

%K nonn,base

%O 1,1

%A _Robert G. Wilson v_, Dec 15 2013

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Last modified November 29 00:31 EST 2023. Contains 367422 sequences. (Running on oeis4.)