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 A195239 Related to FNV primes: Least 0 < m < 256 with 4 or 5 1-bits such that 2^n + 256 + m > 16777600 (mod 1099494850560), or 0 if no such m exists. 1
 147, 55, 47, 47, 39, 23, 89, 47, 45, 43, 39, 77, 0, 31, 23, 53, 179, 43, 71, 103, 75, 29, 117, 197, 59, 23, 89, 77, 39, 31, 89, 55, 147, 71, 143, 169, 59, 109, 47, 103, 51, 205, 209, 139, 89, 29, 47, 29, 167, 205, 107, 47, 0, 61, 53, 103, 87, 53, 83, 85, 71, 143, 51, 43 (list; graph; refs; listen; history; text; internal format)
 OFFSET 24,1 COMMENTS The FNV-primes for n=8*trunc((2^s+5)/12) and s=5..11 are used in FNV hashes: 24, 40, 88, 168, 344, 680, and 1368. a(n) = 0 for almost all n, thus the fraction of bit sizes suitable for the FNV hash is asymptotically smaller than any fixed fraction. In practice this is not an issue since required sizes are small and for large values some nearby size can be chosen instead. - Charles R Greathouse IV, Apr 10 2012 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 24..10000 IETF, The FNV non-cryptographic hash algorithm Landon Curt Noll, Fowler/Noll/Vo (FNV) Hash Wikipedia, Fowler-Noll-Vo hash function EXAMPLE a(24)=147 is binary 10010011, 2^24 + 256 + 147 = 16777619 is prime, and 16777619 > 16777600 (mod 1099494850560). With 24 = 8*trunc((2^5 + 5)/12) this prime is used for 2^5 = 32-bit FNV-hashing. For 2^6 = 64-bit FNV-hashing a(40)=179 with 40 = 8*trunc((64 + 5)/12) determines the FNV-prime 1099511628211. MATHEMATICA a[n_] := Module[{t}, For[m = 15, m <= 241, m++, t = DigitCount[m, 2, 1]; If[t > 3 && t < 6 && PrimeQ[t = m + 2^n + 256] && Mod[t, 1099494850560] > 16777600, Return[m]]]; 0]; Table[a[n], {n, 24, 100}] (* Jean-François Alcover, Oct 10 2017, translated from PARI *) PROG (PARI) a(n)=my(t); for(m=15, 241, t=vecsum(binary(m)); if(t>3&&t<6&& isprime(t=2^n+256+m)&&t%1099494850560>16777600, return(m))); 0 \\ Charles R Greathouse IV, Apr 10 2012 CROSSREFS Sequence in context: A172911 A172933 A145212 * A122064 A320511 A259288 Adjacent sequences: A195236 A195237 A195238 * A195240 A195241 A195242 KEYWORD nonn AUTHOR Frank Ellermann, Sep 13 2011 STATUS approved

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Last modified September 26 17:49 EDT 2023. Contains 365666 sequences. (Running on oeis4.)