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 A002323 M2223 N0882 #36 Jul 09 2023 12:14:39
%S A002323 1,3,1,5,3,15,3,20,1,1,1,32,37,22,36,8,36,10,1,7,49,48,23,77,92,81,13,
%T A002323 95,49,1,17,95,30,96,66,132,67,107,3,50,148,25,52,175,167,109,143,201,
%U A002323 99,30,13,207,200,255,64,260,190,208,159,208,78,98,243,60
%N A002323 ((2^m - 1) / p) mod p, where p = prime(n) and m = ord(2,p).
%C A002323 a(n) = 0 if and only if prime(n) is a Wieferich prime (A001220). - _Eric M. Schmidt_, Feb 23 2015
%D A002323 D. H. Lehmer, Guide to Tables in the Theory of Numbers. Bulletin No. 105, National Research Council, Washington, DC, 1941, pp. 7-10.
%D A002323 W. Meißner, Über die Teilbarkeit von 2^p-2 durch das Quadrat der Primzahl p=1093, Sitzungsberichte der Königlich Preußischen Akadamie der Wissenschaften, Berlin, 35 (1913), 663-667.
%D A002323 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002323 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002323 Eric M. Schmidt, <a href="/A002323/b002323.txt">Table of n, a(n) for n = 2..10000</a>
%H A002323 W. Meissner, <a href="/A001917/a001917.pdf">Über die Teilbarkeit von 2^p-2 durch das Quadrat der Primzahl p = 1093</a>, Sitzungsberichte Königlich Preussischen Akadamie Wissenschaften Berlin, 35 (1913), 663-667. [Annotated scanned copy]
%e A002323 For p = prime(3) = 5, we find that m = 4 is the smallest positive integer for which 2^m - 1 is divisible by p. So a(3) = ((2^4 - 1) / 5) mod 5 = 3. - _Eric M. Schmidt_, Jun 21 2013
%t A002323 Table[p = Prime[n]; Mod[(2^MultiplicativeOrder[2, p] - 1)/p, p], {n, 2, 100}] (* _T. D. Noe_, Jun 21 2013 *)
%o A002323 (Sage) def A002323(n) : p = nth_prime(n); return (2^(Mod(2,p).multiplicative_order()) - 1) // p % p # _Eric M. Schmidt_, Jun 21 2013
%o A002323 (PARI) a(n) = my(p=prime(n));(lift(Mod(2,p^2)^znorder(Mod(2,p)))-1)/p \\ _Jeppe Stig Nielsen_, May 30 2023
%Y A002323 Cf. A001220, A001917.
%K A002323 nonn,easy
%O A002323 2,2
%A A002323 _N. J. A. Sloane_
%E A002323 Proper definition added by and more terms from _Eric M. Schmidt_, Jun 21 2013