A064396 Primes p for which the exponent of the highest power of 2 dividing p! is equal to prevprime(prevprime(p)).

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

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