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A075410
a(n) is the smallest m such that n!!-m and n!!+m are both primes.
2
0, 0, 3, 2, 5, 2, 5, 8, 7, 4, 19, 16, 29, 68, 97, 16, 109, 86, 19, 158, 17, 172, 41, 16, 529, 106, 263, 212, 163, 302, 593, 302, 607, 262, 311, 428, 227, 106, 1271, 8, 229, 386, 1489, 32, 47, 1996, 1097, 2566, 41, 632, 1913, 458, 149, 1244, 2837, 362, 3317, 908
OFFSET
2,3
COMMENTS
For n = 5,7,10,11,22,41,67,76,91,96,163,245,299,341, n!! is an interprime, the average of two consecutive primes, see A075275. See also n^n and n! as average of two primes in A075468 and A075409.
EXAMPLE
a(4) = 3 because 4!! = 8 and 8 -/+ 3 = 5 and 11 are primes with smallest equal distances from 4!!
MATHEMATICA
smbp[n_]:=Module[{m=0, n2=n!!}, While[Total[Boole[PrimeQ[n2+{m, -m}]]] != 2, m++]; m]; Array[smbp, 60, 2] (* Harvey P. Dale, Sep 02 2017 *)
CROSSREFS
Sequence in context: A366687 A154421 A057034 * A023513 A069735 A358536
KEYWORD
nonn
AUTHOR
Zak Seidov, Sep 18 2002
EXTENSIONS
More terms from David Wasserman, Jan 17 2005
STATUS
approved