This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A045526 #22 Jan 05 2025 19:51:35 %S A045526 6,56,80,156,161,170,186,200,230,238,277,288,305,307,323,325,327,344, %T A045526 385,410,451,454,472,475,504,532,547,551,575,592,601,615,645,661,697, %U A045526 710,724,731,790,800,811,822,848 %N A045526 Numbers k such that k! has initial digit '7'. %C A045526 The asymptotic density of this sequence is log_10(8/7) = 0.057991... (Kunoff, 1987). - _Amiram Eldar_, Jul 17 2020 %H A045526 Chai Wah Wu, <a href="/A045526/b045526.txt">Table of n, a(n) for n = 1..10000</a> %H A045526 Sharon Kunoff, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Scanned/25-4/kunoff.pdf">N! has the first digit property</a>, The Fibonacci Quarterly, Vol. 25, No. 4 (1987), pp. 365-367. %H A045526 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a> %F A045526 A008905(a(n)) = 7. - _Amiram Eldar_, Jul 17 2020 %e A045526 6 is a term since 6! = 720 has the initial digit 7. %t A045526 Select[ Range[ 900 ], IntegerDigits[ #! ] [[1]] == 7 & ] %o A045526 (PARI) isok(n) = digits(n!)[1] == 7; \\ _Michel Marcus_, Feb 08 2017 %Y A045526 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. %K A045526 nonn,base %O A045526 1,1 %A A045526 _Jeff Burch_