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A064395 Primes p for which the exponent of the highest power of 2 dividing p! is equal to prevprime(p). 0
5, 23, 71, 83, 101, 113, 197, 281, 353, 359, 373, 401, 599, 683, 739, 751, 773, 977, 1091, 1097, 1103, 1217, 1223, 1229, 1237, 1283, 1553, 1559, 1601, 1607, 1619, 2039, 2347, 2357, 2389, 2417, 2473, 2539, 2671, 2699, 2749, 2857, 3019, 3049, 3499, 3581 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..46.

EXAMPLE

5!=2^3 * 3 * 5, 23!=2^19 * 3^9 * 5^4 * 7^3 * 11^2 * 13 * 17 * 19 * 23, 71!=2^67 * 3^32 * 5^16 * 7^11 * 11^6 * 13^5 * 17^4 * 19^3 * 23^3 * 29^2 * 31^2 * 37 * 41 * 43 * 47 * 53 * 59 * 61 * 67 * 71.

MAPLE

for n from 3 to 10^4 do if sum(floor(n/(2^i)), i=1..15) = prevprime(n) and isprime(n) then printf(`%d, `, n) fi; od:

MATHEMATICA

f[n_] := (t = 0; p = 2; While[s = Floor[n/p]; t = t + s; s > 0, p *= 2]; t); Do[ If[ f[Prime[n]] == Prime[n - 1], Print[ Prime[n]]], {n, 2, 10^3} ]

CROSSREFS

Complement of A064393 relative to A064394.

Sequence in context: A084671 A284648 A243442 * A230497 A138905 A125955

Adjacent sequences:  A064392 A064393 A064394 * A064396 A064397 A064398

KEYWORD

nonn

AUTHOR

Vladeta Jovovic, Sep 29 2001

EXTENSIONS

More terms from James A. Sellers, Oct 01 2001

STATUS

approved

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Last modified February 18 02:20 EST 2018. Contains 299297 sequences. (Running on oeis4.)