A256737 Number of composites lying between successive pairs of primes, beginning with pair (2,3). Bisection of A046933.
0, 1, 1, 1, 5, 5, 1, 5, 1, 3, 5, 5, 3, 3, 3, 3, 1, 1, 5, 5, 1, 1, 1, 11, 1, 5, 9, 5, 1, 3, 9, 3, 3, 5, 1, 5, 5, 3, 7, 7, 1, 1, 3, 7, 1, 11, 3, 3, 11, 17, 9, 5, 5, 5, 1, 5, 1, 9, 3, 5, 11, 5, 9, 9, 5, 3, 5, 7, 13, 11, 9, 3, 9, 3, 3, 3, 3, 3, 9, 3, 5, 3, 5, 5, 3, 1, 1, 9, 9, 5, 3, 3, 5, 5, 21
Offset: 1
Keywords
Examples
For the third term in the sequence, use prime pair (11,13). Only composite that lies between is "12", thus the third value in the sequence is "1".
Programs
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Mathematica
Flatten[Differences/@Partition[Prime[Range[200]],2]]-1 (* Harvey P. Dale, Dec 17 2023 *)
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PARI
a(n)=my(q=prime(2*n)); q-precprime(q-1)-1 \\ Charles R Greathouse IV, Apr 21 2015