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 A051464 #13 Sep 16 2021 02:26:12 %S A051464 2,2,2,2,4,4,2,2,4,2,4,2,4,6,4,4,16,2,4,2,4,2,4,8,12,8,2,4,8,4,4,4,4, %T A051464 4,4,8,8,4,8,16,8,4,8,8,6,16,8,8,8,16,8,4,32,32,8,4,8,4,4,8,16,8,8,16, %U A051464 48,16,16,8,4,16,4,16,16,8,8,8,16,16,8,16,32 %N A051464 Number of divisors of 4*(2^n-1) + 1. %C A051464 Create a table with tau(2^n-1) as the first row (A046801) and tau(m) as the first column (A000005). The second column is tau(A004760) and so on. Rows 2, 3 and 4 are easily described in terms of row 1. This sequence is row 5. %H A051464 Sean A. Irvine, <a href="/A051464/b051464.txt">Table of n, a(n) for n = 1..591</a> %F A051464 a(n) = tau(4*(2^n -1)+1), where d(n) = A000005(n). %t A051464 Array[DivisorSigma[0, 4*(2^# - 1) + 1] &, 81] (* _Michael De Vlieger_, Sep 15 2021 *) %o A051464 (PARI) a(n) = numdiv(4*(2^n-1) + 1); \\ _Michel Marcus_, Sep 16 2021 %Y A051464 Cf. A000005, A036563. %K A051464 nonn %O A051464 1,1 %A A051464 Edwin D. Evans, eevans2(AT)pacbell.net %E A051464 a(81) corrected by _Sean A. Irvine_, Sep 15 2021