A057034 Difference between n!! and the first prime before n!! - 1.

3, 2, 5, 2, 5, 4, 7, 4, 7, 4, 23, 2, 19, 2, 97, 2, 19, 64, 17, 62, 19, 4, 17, 58, 23, 64, 157, 122, 47, 106, 47, 4, 29, 146, 31, 64, 29, 8, 71, 8, 43, 32, 31, 128, 67, 122, 41, 2, 37, 146, 137, 122, 191, 142, 59, 128, 71, 284, 109, 274, 101, 218, 97, 32, 83, 158, 53, 166

Offset

4,1

Comments

Analogous to the lesser Fortunate numbers but unlike them, all entries are not prime. Must odd entries are powers of two and all even entries are primes.

Links

Table of n, a(n) for n=4..71.

Mathematica

PrevPrime[ n_Integer ] := (k=n-1; While[ !PrimeQ[ k ], k-- ]; Return[ k ]); f[ n_Integer ] := (p = n!! - 1; q = PrevPrime[ p ]; Return[ p - q + 1 ]); Table[ f[ n ], {n, 4, 75} ]

Crossrefs

Cf. A006882, A057019.

Sequence in context: A112528 A366687 A154421 * A075410 A023513 A069735

Adjacent sequences: A057031 A057032 A057033 * A057035 A057036 A057037

Keyword

nonn

Author

Robert G. Wilson v, Sep 09 2000

Status

approved