cp's OEIS Frontend

A169669 (first digit of n) * (last digit of n) in decimal representation.

%I A169669 #13 Jul 13 2022 02:07:56
%S A169669 0,1,4,9,16,25,36,49,64,81,0,1,2,3,4,5,6,7,8,9,0,2,4,6,8,10,12,14,16,
%T A169669 18,0,3,6,9,12,15,18,21,24,27,0,4,8,12,16,20,24,28,32,36,0,5,10,15,20,
%U A169669 25,30,35,40,45,0,6,12,18,24,30,36,42,48,54,0,7,14,21,28,35,42,49,56,63,0
%N A169669 (first digit of n) * (last digit of n) in decimal representation.
%C A169669 a(n) = A000030(n)*A010879(n);
%C A169669 a(n) = A115300(n) for n<=100, A115300(101) = 0;
%C A169669 a(n) = A111707(n) for n<=109, A111707(110) = 1;
%C A169669 0 <= a(n) <= 81, range = A174995;
%C A169669 a(10*n + n mod 10) = a(n);
%C A169669 a(A008592(n)) = 0;
%C A169669 A000030(a(A017281(n))) = A000030(A017281(n));
%C A169669 a(n) = a(A004086(n))*A168184(n);
%H A169669 Reinhard Zumkeller, <a href="/A169669/b169669.txt">Table of n, a(n) for n = 0..10000</a>
%o A169669 (Haskell)
%o A169669 a169669 n = a000030 n * mod n 10
%o A169669 -- _Reinhard Zumkeller_, Apr 29 2015
%o A169669 (Python)
%o A169669 def a(n): return int(str(n)[0])*(n%10)
%o A169669 print([a(n) for n in range(81)]) # _Michael S. Branicky_, Jul 13 2022
%Y A169669 Cf. A088133.
%Y A169669 Cf. A000030, A008592, A010879, A111707, A115300, A174995.
%K A169669 base,nonn,hear,look
%O A169669 0,3
%A A169669 _Reinhard Zumkeller_, Apr 05 2010