OFFSET
1,1
COMMENTS
EXAMPLE
For p=3, p + (p^2-1)/8 = 4 = 2^2. For p=19, p + (p^2-1)/8 = 64 = 8^2. For p=211, p + (p^2-1)/8 = 5776 = 76^2.
MAPLE
A077241 := proc(n) if n <= 3 then op(n+1, [1, 2, 8, 13]) ; else 6*procname(n-2)-procname(n-4) ; fi; end:
for n from 0 do s := A077241(n) ; p := sqrt(17+8*s^2)-4 ; if isprime(p) then printf("%d, \n", p) ; fi; od: # R. J. Mathar, Sep 21 2009
a := proc (n) if isprime(n) = true and type(sqrt(n+(1/8)*n^2-1/8), integer) = true then n else end if end proc; seq(a(n), n = 1 .. 10000000); # Emeric Deutsch, Sep 21 2009
MATHEMATICA
p = 2; lst = {}; While[p < 10^12, If[ IntegerQ@ Sqrt[p + (p^2 - 1)/8], AppendTo[lst, p]; Print@p]; p = NextPrime@p] (* Robert G. Wilson v, Sep 30 2009 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Sep 16 2009
EXTENSIONS
6 more terms from R. J. Mathar, Sep 21 2009
STATUS
approved