A391871 - OEIS

%I #19 Jan 03 2026 06:25:47

%S 1,2,12,21,24,27,71,407,425,447,567,1073,1151,1643,2729,3947,5277,

%T 5393,9665,14123,17309,21827,28551,30113,33633,42749,45737,50177,

%U 75755,83213,126737,145577,168011,172593,251231,281765,334715,408749,483539,523005,542297,672461

%N Indices of records in A210693.

%F A210693(a(n)) = A391870(n).

%t A210693[n_] := Module[{k = 0}, While[++k == n || PowerMod[n, k, 2*k + 1] != PowerMod[k, n, #]] & [2*n + 1]; k];

%t Module[{rec = 0}, Table[If[# > rec, rec = #; m, Nothing] & [A210693[m]], {m, 10000}]]

%Y Cf. A210693, A391870.

%K nonn

%O 1,2

%A _Paolo Xausa_, Dec 21 2025

%E a(27)-a(36) from _Michael S. Branicky_, Dec 22 2025

%E a(37)-a(42) from _Jinyuan Wang_, Jan 03 2026