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A064396 Primes p for which the exponent of the highest power of 2 dividing p! is equal to prevprime(prevprime(p)). 1
317, 467, 619, 1303, 1307, 1429, 1433, 1489, 1613, 1699, 1873, 2713, 2719, 2797, 2971, 3307, 3541, 3769, 4937, 5087, 5233, 5443, 5479, 5507, 5527, 5653, 5657, 5749, 6047, 6143, 6571, 7487, 7547, 7583, 8017, 8431, 8867, 9007, 9931 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

317!=2^311 * 3^155 * 5^77 * 7^51 * 11^30 * 13^25 * 17^19 * 19^16 * 23^13 * 29^10 * 31^10 * 37^8 * 41^7 * 43^7 * 47^6 * 53^5 * 59^5 * 61^5 * 67^4 * 71^4 * 73^4 * 79^4 * 83^3 * 89^3 * 97^3 * 101^3 * 103^3 * 107^2 * 109^2 * 113^2 * 127^2 * 131^2 * 137^2 * 139^2 * 149^2 * 151^2 * 157^2 * 163 * 167 * 173 * 179 * 181 * 191 * 193 * 197 * 199 * 211 * 223 * 227 * 229 * 233 * 239 * 241 * 251 * 257 * 263 * 269 * 271 * 277 * 281 * 283 * 293 * 307 * 311 * 313 * 317.

MAPLE

r:= 1: q:= 2: p:= 3: count:= 0: Res:= NULL:

while count < 100 do

  r:= q; q:= p; p:= nextprime(p);

  if add(floor(p/2^i), i=1..ilog2(p)) = r

    then count:= count+1; Res:= Res, p;

  fi

od:

Res; # Robert Israel, Mar 14 2018

PROG

(PARI) isok(p) = (precprime(precprime(p-1)-1) == factor(p!)[1, 2]) \\ Michel Marcus, Jun 17 2013

CROSSREFS

Sequence in context: A101112 A012871 A142003 * A243958 A273804 A142130

Adjacent sequences:  A064393 A064394 A064395 * A064397 A064398 A064399

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Sep 29 2001

STATUS

approved

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Last modified August 20 03:33 EDT 2019. Contains 326139 sequences. (Running on oeis4.)