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 A385074 #18 Jun 27 2025 00:37:49
%S A385074 1,2,20737,4,9,6,3763,20,40369,35,2951,16,35622023,27,2041,49,25,42,
%T A385074 697,2168,18537061,31958,117,66,356698651,147,7863277,28
%N A385074 Index of the first occurrence of n in A385073.
%C A385074 a(28) if it exists exceeds 10^11.
%C A385074 Although the parity of n and a(n) are often the opposite, it is not a requirement. Cases in point, n = {9, 13, 15, 25}.
%t A385074 f[n_] := Block[{b = 2}, While[GCD[n, b] > 1, b++]; PowerMod[b, n - 1, n]]; k = 1; t[_] := 0; While[ k < 10^10, a = f@k; If[ a < 1001 && t[a] == 0, t[a] = k]; k++]; t /@ Range[0, 27]
%o A385074 (PARI) f(n) = forprime(p=2, , if(n%p, return(lift(Mod(p, n)^(n-1))))); \\ A385073
%o A385074 a(n) = my(k=1); while (f(k) != n, k++); k; \\ _Michel Marcus_, Jun 18 2025
%Y A385074 Cf. A385073.
%K A385074 nonn,more
%O A385074 0,2
%A A385074 _Robert G. Wilson v_, Jun 16 2025