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

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, 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, 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

Offset: 0

Author

Reinhard Zumkeller, Apr 05 2010

Keywords

• base
• nonn
• hear
• look

Comments

a(n) = A000030(n)*A010879(n);

a(n) = A115300(n) for n<=100, A115300(101) = 0;

a(n) = A111707(n) for n<=109, A111707(110) = 1;

0 <= a(n) <= 81, range = A174995;

a(10*n + n mod 10) = a(n);

a(A008592(n)) = 0;

A000030(a(A017281(n))) = A000030(A017281(n));

a(n) = a(A004086(n))*A168184(n);

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 0..10000

Crossrefs

Cf. A088133.

Cf. A000030, A008592, A010879, A111707, A115300, A174995.

Programs

Haskell

a169669 n = a000030 n * mod n 10
-- Reinhard Zumkeller, Apr 29 2015

Python

def a(n): return int(str(n)[0])*(n%10)
print([a(n) for n in range(81)]) # Michael S. Branicky, Jul 13 2022