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 A071169 a(n) is the smallest number k such that prime(k) == 2*n-1 (mod phi(k)). 2
 3, 5, 7, 15, 22, 17, 19, 48, 23, 41, 82, 39, 29, 47, 77, 94, 53, 91, 112, 69, 81, 61, 59, 101, 189, 142, 103, 85, 107, 109, 203, 354, 148, 95, 1122, 158, 169, 141, 119, 127, 166, 241, 226, 491, 131, 125, 137, 185, 251, 393, 242, 133, 332, 139, 244, 340, 402 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS From Michael De Vlieger, Feb 16 2017: (Start) Records and position of records:          3       1          5       2          7       3         15       4         22       5         48       8         82      11         94      16        112      19        189      25        203      31        354      32       1122      35       1223      74       1234     103       4244     104       6718     137      12218     200      16304     218      19540     248      74478     263    1014994     323    2801012    1268   16829184    1913   16903906    2213 a(2468) is larger than 10^8. (End) LINKS Michael De Vlieger and Michel Marcus, Table of n, a(n) for n = 1..2467 (First 262 terms from Michel Marcus), Feb 16 2017 FORMULA a(n) = Min_{k} A071168(k) = 2*n-1. EXAMPLE n=5, a(5)=22, prime(22)=79, Phi[22]=10, Mod[79,10]=9=2n-1=5. MATHEMATICA f[x_] := Mod[Prime[x], EulerPhi[x]] t=Table[0, {256}]; Do[s=f[n]; If[s<257&&t[[s]]==0, t[[s]]=n], {n, 1, 100000}]; t (* Second program: *) Table[x = 1; While[Mod[Prime@ x, EulerPhi@ x] != 2 n - 1, x++]; x, {n, 57}] (* Michael De Vlieger, Feb 13 2017 *) PROG (PARI) a(n) = {my(x = 1); while (prime(x) % eulerphi(x) != 2*n-1, x++); x; } \\ Michel Marcus, Feb 13 2017 CROSSREFS Cf. A000040, A000010, A066936, A071168. Sequence in context: A018286 A194360 A057743 * A172235 A163979 A124248 Adjacent sequences:  A071166 A071167 A071168 * A071170 A071171 A071172 KEYWORD nonn AUTHOR Labos Elemer, May 15 2002 STATUS approved

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Last modified September 20 17:42 EDT 2021. Contains 347588 sequences. (Running on oeis4.)