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 A382720 #21 Aug 16 2025 15:28:57 %S A382720 1,2,3,4,5,6,7,2,4,6,8,10,12,14,3,6,9,12,15,18,21,4,8,12,16,20,24,28, %T A382720 5,10,15,20,25,30,35,6,12,18,24,30,36,42,7,14,21,28,35,42,49,2,4,6,8, %U A382720 10,12,14,4,8,12,16,20,24,28,6,12,18,24,30,36,42,8,16,24,32,40,48,56,10,20,30,40 %N A382720 Number of entries in the n-th row of Pascal's triangle not divisible by 7. %H A382720 Hsien-Kuei Hwang, Svante Janson, and Tsung-Hsi Tsai, <a href="https://arxiv.org/abs/2408.06817">Periodic minimum in the count of binomial coefficients not divisible by a prime</a>, arXiv:2408.06817 [math.NT], 2024. %t A382720 a[n_] := Times @@ (IntegerDigits[n, 7] + 1);Array[a,81,0] (* _James C. McMahon_, Aug 16 2025 *) %o A382720 (Python) %o A382720 from math import prod %o A382720 from gmpy2 import digits %o A382720 def A382720(n): return prod(int(d)+1 for d in digits(n,7)) # _Chai Wah Wu_, Aug 10 2025 %Y A382720 Cf. A001316, A006047, A194459, A382721-A382722, A382726. %K A382720 nonn %O A382720 0,2 %A A382720 _N. J. A. Sloane_, Apr 23 2025