cp's OEIS Frontend

A077327 Smallest number beginning with 2 and having exactly n distinct prime divisors.

%I A077327 #9 Feb 21 2021 02:29:19
%S A077327 2,20,204,210,2310,200970,2012010,20030010,223092870,20090100030,
%T A077327 200560490130,20055767721990,2000029432190790,20384767656323070,
%U A077327 2000848249650860610,200001648981983238390,2183473617971732996910
%N A077327 Smallest number beginning with 2 and having exactly n distinct prime divisors.
%e A077327 a(1) = 2, a(5) = 2310 = 2*3*5*7*11.
%o A077327 (Python)
%o A077327 from sympy import primorial, factorint
%o A077327 def a(n, begins_with=2): # use begins_with 1-9 for A077326-A077334
%o A077327   m, start_digit = primorial(n), str(begins_with)
%o A077327   while len(factorint(m)) != n or str(m)[0] != start_digit:
%o A077327     m += 1
%o A077327     s = str(m)
%o A077327     if s[0] == start_digit: continue
%o A077327     elif s[0] < start_digit: m = int(start_digit+'0'*(len(s)-1))
%o A077327     else: m = int(start_digit+'0'*len(s))
%o A077327   return m
%o A077327 print([a(n) for n in range(1, 10)]) # _Michael S. Branicky_, Feb 20 2021
%Y A077327 Cf. A077326, A077328, A077329, A077330, A077331, A077332, A077333, A077334.
%Y A077327 Cf. A106411-A106419, A106421-A106429.
%K A077327 base,nonn
%O A077327 1,1
%A A077327 _Amarnath Murthy_, Nov 04 2002
%E A077327 Correct a(2) and a(3), add a(6)-a(11) from _Ray Chandler_, Apr 17 2005
%E A077327 More terms from _Ray Chandler_, May 02 2005