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A045526 Numbers k such that k! has initial digit '7'. 18
6, 56, 80, 156, 161, 170, 186, 200, 230, 238, 277, 288, 305, 307, 323, 325, 327, 344, 385, 410, 451, 454, 472, 475, 504, 532, 547, 551, 575, 592, 601, 615, 645, 661, 697, 710, 724, 731, 790, 800, 811, 822, 848 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The asymptotic density of this sequence is log_10(8/7) = 0.057991... (Kunoff, 1987). - Amiram Eldar, Jul 17 2020
LINKS
Sharon Kunoff, N! has the first digit property, The Fibonacci Quarterly, Vol. 25, No. 4 (1987), pp. 365-367.
FORMULA
A008905(a(n)) = 7. - Amiram Eldar, Jul 17 2020
EXAMPLE
6 is a term since 6! = 720 has the initial digit 7.
MATHEMATICA
Select[ Range[ 900 ], IntegerDigits[ #! ] [[1]] == 7 & ]
PROG
(PARI) isok(n) = digits(n!)[1] == 7; \\ Michel Marcus, Feb 08 2017
CROSSREFS
For factorials with initial digit d (1 <= d <= 9) see A045509, A045510, A045511, A045516, A045517, A045518, A282021, A045519; A045520, A045521, A045522, A045523, A045524, A045525, A045526, A045527, A045528, A045529. See also A000142, A008905.
Sequence in context: A335217 A335199 A137033 * A164579 A137034 A177059
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)