OFFSET
1,1
COMMENTS
Also primes equal to the arithmetic mean between product of two consecutive primes and prime p.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
a(2)=11 because 11=(3*5+7)/2 and p is 7;
a(3)=23 because 23=(5*7+11)/2 and p is 11;
a(4)=47 because 47=(7*11+17)/2 and p is 17;
a(5)=83 because 83=(11*13+23)/2 and p is 23.
MATHEMATICA
a[2] = 11; a[n_] := a[n] = Block[{k = PrimePi[2a[n - 1] - Prime[n - 1]Prime[n]] + 1, q = Prime[n]Prime[n + 1]}, While[p = Prime[k]; !PrimeQ[(q + p)/2], k++ ]; (q + p)/2]; Table[ a[n], {n, 2, 43}] (* Robert G. Wilson v, Nov 29 2004 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Teofilatto, Nov 28 2004
EXTENSIONS
Edited and extended by Robert G. Wilson v, Nov 29 2004
STATUS
approved