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A348549 Number of positive integers with n digits that are the product of two integers ending with 8. 2
0, 1, 14, 195, 2200, 24013, 255969, 2687317, 27934809, 288342379, 2960920297, 30285890402, 308834717932, 3141625339760, 31895159990436 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) is the number of n-digit numbers in A348548.

LINKS

Table of n, a(n) for n=1..15.

FORMULA

a(n) < A052268(n).

Conjecture: lim_{n->infinity} a(n)/a(n-1) = 10.

PROG

(Python)

def a(n):

lo, hi = 10**(n-1), 10**n

return len(set(a*b for a in range(8, hi//8+1, 10) for b in range(a, hi//a+1, 10) if lo <= a*b < hi))

print([a(n) for n in range(1, 9)]) # Michael S. Branicky, Oct 22 2021

CROSSREFS

Cf. A052268, A348548.

Cf. A346509 (ending with 1), A346629 (ending with 2), A346952 (ending with 3), A347255 (ending with 4), A337855 (ending with 5), A337856 (ending with 6), A348055 (ending with 7).

Sequence in context: A275084 A086946 A158530 * A171319 A007655 A208383

Adjacent sequences: A348546 A348547 A348548 * A348550 A348551 A348552

KEYWORD

nonn,base,hard,more

AUTHOR

Stefano Spezia, Oct 22 2021

EXTENSIONS

a(9)-a(10) from Michael S. Branicky, Oct 22 2021

a(11)-a(15) from Martin Ehrenstein, Nov 06 2021

STATUS

approved

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Last modified November 28 22:51 EST 2022. Contains 358421 sequences. (Running on oeis4.)