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A092111 a(n) = n+1 minus the greatest number of 1's in the binary representations of primes between 2^n and 2^(n+1). 2
0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 2, 1, 0, 1, 0, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 0, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 0, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 0, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,14

COMMENTS

0's occur only at Mersenne prime exponents (A000043) - 1, twos are in A092112, threes do not appear < 504.

a(n) <= 2 for n <= 2000. - Robert Israel, Mar 05 2020

LINKS

Robert Israel, Table of n, a(n) for n = 1..2000

FORMULA

a(n) = n+1 - A091937(n).

MAPLE

f:= proc(n) local t, j, k;

  t:= 2^(n+1)-1;

  if isprime(t) then return 0 fi;

  for j from 1 to n-1 do if isprime(t-2^j) then return 1 fi od;

  for j from 1 to n-2 do for k from j+1 to n-1 do

    if isprime(t-2^j-2^k) then return 2 fi od od;

  FAIL

end proc:

map(f, [$1..200]); # Robert Israel, Mar 05 2020

MATHEMATICA

Compute the second line of the Mathematica code for A091938, then (Table[n + 1, {n, 105}]) - (Count[ IntegerDigits[ #, 2], 1] & /@ Table[ f[n], {n, 105}])

CROSSREFS

Cf. A091938, A092112.

Sequence in context: A330262 A098055 A344739 * A330167 A307776 A341027

Adjacent sequences:  A092108 A092109 A092110 * A092112 A092113 A092114

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Feb 20 2004

STATUS

approved

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Last modified June 22 04:06 EDT 2021. Contains 345367 sequences. (Running on oeis4.)