

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
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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.


LINKS

Table of n, a(n) for n=2..59.


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

Cf. A075275, A075468 and A075409.
Sequence in context: A112528 A154421 A057034 * A023513 A069735 A274457
Adjacent sequences: A075407 A075408 A075409 * A075411 A075412 A075413


KEYWORD

nonn


AUTHOR

Zak Seidov, Sep 18 2002


EXTENSIONS

More terms from David Wasserman, Jan 17 2005


STATUS

approved



