=7;
a[n_]:=Sum[(Floor[a[n-1]/10^k]-10*Floor[a[n-1]/10^(k+1)]) ^ (2) , {k, 0,
Floor[Log[10, a[n-1]]] }]
Table[a[n], {n, 1, 10}] (* José de Jesús Camacho Medina, Mar 29 2014 *)
PROG
(Haskell)
a007770 n = a007770_list !! (n-1)
a007770_list = filter ((== 1) . a103369) [1..]
-- Reinhard Zumkeller, Aug 24 2011
(PARI) ssd(n)=n=digits(n); sum(i=1, #n, n[i]^2)
is(n)=while(n>6, n=ssd(n)); n==1 \\ Charles R Greathouse IV, Nov 20 2012
(Python)
def ssd(n): return sum(int(d)**2 for d in str(n))
def ok(n):
while n not in [1, 4]: n = ssd(n) # iterate until fixed point or in cycle
return n==1
def aupto(n): return [k for k in range(1, n+1) if ok(k)]
print(aupto(338)) # Michael S. Branicky, Jan 07 2021
باشگاهها
Niger Team
۲۱۸ عضو