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 A294389 #29 Jan 11 2023 15:59:59 %S A294389 1,2,4,2,2,0,1,8,3,8,10,4,1,0,13,8,5,12,1,6,6,8,4,20,10,16,22,8,8,0,1, %T A294389 26,11,8,28,10,1,32,31,8,11,24,19,12,12,32,16,28,1,28,40,44,26,32,1, %U A294389 44,15,32,46,16,1,0,4,8,17,36,1,58,18,8,55,56,46,40,60,8,20,32,10,62,21,8,4,22 %N A294389 a(n) = 2^(n-3) mod n, for n >= 3. %C A294389 Every nonnegative integer seems to appear in the sequence, and every integer seems to appear in the sequence of first differences (see link). %C A294389 For all 3 <= n < 10^9, a(n) != 7. - _Robert G. Wilson v_, Nov 30 2017 %H A294389 G. C. Greubel, <a href="/A294389/b294389.txt">Table of n, a(n) for n = 3..10000</a> %H A294389 Enrique Navarrete, <a href="/A294389/a294389.pdf">Sequences Derived from Residues of 2^n (mod n)</a> %t A294389 Array[PowerMod[2, # - 3, #] &, 80, 3] (* _Robert G. Wilson v_, Nov 30 2017 *) %o A294389 (Magma) [Modexp(2,(n-3),n): n in [3..100]]; // _G. C. Greubel_, Jan 11 2023 %o A294389 (SageMath) [power_mod(2,(n-3),n) for n in range(3,101)] # _G. C. Greubel_, Jan 11 2023 %Y A294389 Cf. A015910, A212844, A213859. %K A294389 nonn %O A294389 3,2 %A A294389 _Enrique Navarrete_, Oct 29 2017 %E A294389 More terms from _Robert G. Wilson v_, Nov 30 2017