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 A244249 Table A(n,k) in which n-th row lists in increasing order all bases b to which p = prime(n) is a Wieferich prime (i.e., b^(p-1) is congruent to 1 mod p^2), read by antidiagonals. 15
 5, 9, 8, 13, 10, 7, 17, 17, 18, 18, 21, 19, 24, 19, 3, 25, 26, 26, 30, 9, 19, 29, 28, 32, 31, 27, 22, 38, 33, 35, 43, 48, 40, 23, 40, 28, 37, 37, 49, 50, 81, 70, 65, 54, 28, 41, 44, 51, 67, 94, 80, 75, 62, 42, 14, 45, 46, 57, 68, 112, 89, 110, 68, 63, 41, 115 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Alois P. Heinz, Rows n = 1..141, flattened EXAMPLE Table starts with: p =  2:   5,  9, 13, 17,  21,  25,  29,  33, ... p =  3:   8, 10, 17, 19,  26,  28,  35,  37, ... p =  5:   7, 18, 24, 26,  32,  43,  49,  51, ... p =  7:  18, 19, 30, 31,  48,  50,  67,  68, ... p = 11:   3,  9, 27, 40,  81,  94, 112, 118, ... p = 13:  19, 22, 23, 70,  80,  89,  99, 146, ... p = 17:  38, 40, 65, 75, 110, 131, 134, 155, ... MAPLE A:= proc(n, k) option remember; local p, b;       p:= ithprime(n);       for b from 1 +`if`(k=1, 1, A(n, k-1))         while b &^ (p-1) mod p^2<>1       do od; b     end: seq(seq(A(n, 1+d-n), n=1..d), d=1..14);  # Alois P. Heinz, Jul 02 2014 MATHEMATICA A[n_, k_] := A[n, k] = Module[{p, b}, p = Prime[n]; For[b = 1 + If[k == 1, 1, A[n, k-1]], PowerMod[b, p-1, p^2] != 1, b++]; b]; Table[Table[A[n, 1+d-n], {n, 1, d}], {d, 1, 14}] // Flatten (* Jean-François Alcover, Mar 09 2015, after Alois P. Heinz *) PROG (PARI) forprime(p=2, 10^1, print1("p=", p, ": "); for(a=2, 10^2, if(Mod(a, p^2)^(p-1)==1, print1(a, ", "))); print("")) CROSSREFS Cf. A001220, A185103. First column of table is A039678. Main diagonal gives A280721. Sequence in context: A077771 A019754 A315120 * A353602 A123600 A063623 Adjacent sequences:  A244246 A244247 A244248 * A244250 A244251 A244252 KEYWORD nonn,tabl AUTHOR Felix Fröhlich, Jun 23 2014 STATUS approved

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Last modified August 8 10:26 EDT 2022. Contains 356009 sequences. (Running on oeis4.)