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A191474 Smallest prime  q such that q + prime(n) is a power of 2. 2
2, 5, 3, 549755813881, 5, 3, 47, 13, 41, 3, 97, 2011, 23, 536870869, 17, 11, 5, 3, 61, 953, 439, 433, 173, 167, 31, 67108763, 409, 149, 19, 911, 140737488355201, 16253, 887, 373, 107, 2147483497, 32611, 349, 89, 83, 3917, 331, 16193, 2096959, 59, 313, 33554221 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding exponents of 2: 2, 3, 3, 39, 4, 4, 6, 5, 6, 5, 7, 11, 6, 29, 6, 6, 6, 6, 7, 10, 9, 9, 8, 8, 7, 1, 9, 8, 7, 10, 47, 14, 10, 9, 8, 31, 15, 9, 8, 8, 12, 9, 14, 21, 8, 9, 1, ...

LINKS

Robert Israel, Table of n, a(n) for n = 1..285

EXAMPLE

2+2 = 2^2, 3+5 = 2^3, 5+3 = 2^3, 7+549755813881 = 2^39, 11+5 = 2^4.

MAPLE

f:= proc(n) local p, m, t, q;

  p:= ithprime(n);

  for t from ilog2(p) do

    q:= 2^t - p;

    if isprime(q) then return q fi;

  od;

end proc:

map(f, [$1..50]); # Robert Israel, Dec 23 2020

CROSSREFS

Sequence in context: A239309 A077073 A307126 * A199602 A324057 A106315

Adjacent sequences:  A191471 A191472 A191473 * A191475 A191476 A191477

KEYWORD

nonn

AUTHOR

Zak Seidov, Aug 28 2012

EXTENSIONS

a(26) corrected by Robert Israel, Dec 23 2020

STATUS

approved

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Last modified January 21 12:13 EST 2022. Contains 350477 sequences. (Running on oeis4.)