%N Smallest member p of a triple of primes (p,p+8,p+20).
%C A subsequence of A023202. The definition implies that the sum of the first two primes, 2(p+4), divides the sum of the product of the first two primes and the last, p(p+8)+p+20=(p+4)(p+5). This feature is shared with A022005 and common to prime triples of the format (p,p+2*a,p+a+a^2) with even a. - _R. J. Mathar_, Apr 26 2007
%p isA128928 := proc(n) isprime(n) and isprime(n+8) and isprime(n+20) ; end: for n from 1 to 300 do if isA128928(ithprime(n)) then printf("%d,",ithprime(n)) ; fi ; od ; # _R. J. Mathar_, Apr 26 2007
%t kmax = 580; Select[ Prime[ Range[1, kmax] ], (PrimeQ[ # + 8] && PrimeQ[ # + 20])& ] (* _Stuart Clary_ *)
%Y Cf. A022005.
%A _J. M. Bergot_, Apr 25 2007
%E Corrected and extended by _Robert G. Wilson v_, _R. J. Mathar_ and _Stuart Clary_, Apr 26 2007