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A176451
Number of primes between two consecutive nonprimes in A037143.
2
2, 1, 1, 0, 2, 0, 2, 0, 1, 0, 2, 0, 0, 1, 0, 2, 1, 0, 1, 0, 0, 2, 0, 1, 2, 0, 1, 1, 0, 0, 1, 0, 0, 0, 3, 2, 1, 0, 0, 0, 0, 0, 1, 1, 0, 2, 0, 0, 0, 0, 2, 1, 0, 0, 1, 1, 1, 0, 2, 0, 0, 2, 2, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 3, 0, 2, 0, 1, 0, 1, 0, 1, 0, 2, 1, 2, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 2, 1, 0, 0, 0, 0
OFFSET
1,1
COMMENTS
2 together with the number of primes between successive semiprimes.
LINKS
FORMULA
a(n) = A088700(n-1) for n >= 2.
EXAMPLE
a(1) = 2 because A037143(1) = 1 (nonprime) < A037143(2) = 2 (prime) < A037143(3) = 3 (prime) < A037143(4) = 4 (nonprime).
MATHEMATICA
Join[{2}, -1 + Differences[Position[Select[PrimeOmega[Range[400]], # < 3 &], 2] // Flatten]] (* Amiram Eldar, Sep 07 2024 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved