A065047 -id:A065047 - cp's OEIS frontend

A232068 Least k such that prime(n) + 2^(k+L) is a prime, where L is the length of binary representation of prime(n): L = A070939(A000040(n)). a(n)=-1 if no such k exists.

0, 0, 1, 1, 0, 8, 1, 2, 0, 7, 0, 5, 0, 203, 1, 3, 2, 3, 0, 3, 3, 0, 2, 1, 0, 1, 2, 7, 0, 1, 1, 5, 2, 1, 8, 2, 0, 501, 3, 1, 8, 3, 0, 1, 2, 0, 0, 1, 22, 3, 1, 4, 5, 0, 2, 4, 11, 1, 6, 1, 2, 5, 0, 3, 0, 7, 1, 0, 1, 18, 8, 3, 13, 5, 6, 2, 3, 34, 1, 2, 3, 4, 19, 5, 6, 4, 1

Offset: 2

Alex Ratushnyak, Nov 17 2013

Prime(n) is in A065047 if and only if a(n)=0.

Cf. A000040, A070939, A065047, A094076.

A232084 Least k such that prime(n) + 2^(k+L) - 2^L is a prime, where L is the length of binary representation of prime(n): L = A070939(A000040(n)). a(n) = -1 if no such k exists.

Original entry on oeis.org

1, 1, 2, 2, 1, 2, 4, 4, 1, 2, 1, 2, 1, 2, 4, 2, 3, 4, 1, 2, 2, 1, 5, 4, 1, 2, 2, 4, 1, 6, 18, 20, 2, 4, 2, 3, 1, 4, 2, 2, 3, 6, 1, 12, 2, 1, 1, 96, 2, 4, 4, 2, 2, 1, 3, 3, 4, 6, 6, 4, 3, 6, 1, 4, 1, 2, 2, 1, 56, 2, 3, 8, 4, 4, 3, 4, 2, 4, 4, 3, 4, 4, 18, 20, 2, 8, 2, 2

Offset: 2

Alex Ratushnyak, Nov 17 2013

Least number of 1's that must be prepended to the binary representation of prime(n) such that the result is another prime.

Prime(n) is in A065047 if and only if a(n) = 1.

			a(6) = 1 because 13 in binary is 1101, and 29 (11101 in binary) is a prime.
a(7) = 2 because 17 in binary is 10001, and 113 (1110001 in binary) is a prime.
a(8) = 4 because 19 in binary is 10011, and 499 (111110011 in binary) is a prime.

Cf. A000040, A070939, A065047, A094076, A023758.

cp's OEIS Frontend

A232068 Least k such that prime(n) + 2^(k+L) is a prime, where L is the length of binary representation of prime(n): L = A070939(A000040(n)). a(n)=-1 if no such k exists.

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