OFFSET
1,1
COMMENTS
The parity of k is opposite to the parity of the differences.
EXAMPLE
5 is a term because 5!! = 15 is the average of two successive primes, 13 and 17;
163 is a term because 163!! is the average of two successive primes, 163!! -+ 128.
MATHEMATICA
PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k] Do[ a = n!!; If[ 2a == PrevPrim[a] + NextPrim[a], Print[n]], {n, 3, 762}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Zak Seidov, Sep 12 2002
EXTENSIONS
Edited, corrected and extended by Robert G. Wilson v, Sep 16 2002
STATUS
approved