A115300 Greatest digit of n * least digit of n.

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, 8

Offset: 1

Author

Rick L. Shepherd, Jan 20 2006

Keywords

• base
• nonn
• look

Comments

a(101) = 0 and A111707(101) = 1, but all previous terms match.

a(n) = A169669(n) for n <= 100.

Examples

			a(3) = 3 * 3 = 9, a(232) = 3 * 2 = 6, a(1889009898) = 9 * 0 = 0.
		

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A037904 (greatest-least), A115299 (greatest+least), A111707.

Cf. A054054, A054055, A169669.

Programs

Haskell

a115300 n = a054054 n * a054055 n  -- Reinhard Zumkeller, Apr 29 2015

Mathematica

Array[Max[#] * Min[#] &@ IntegerDigits[#] &, 81] (* James C. McMahon, Aug 18 2024 *)

PARI

a(n) = my(d=digits(n)); vecmin(d)*vecmax(d); \\ Michel Marcus, Aug 18 2024

Python

def a(n): d = list(map(int, str(n))); return max(d) * min(d)
print([a(n) for n in range(1, 82)]) # Michael S. Branicky, Dec 12 2023

Formula

a(n) = A054054(n)*A054055(n). - Reinhard Zumkeller, Apr 29 2015