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 A249162 Square array A(p, b) read by antidiagonals in which rows are indexed by successive prime numbers p_i and row b(p_i) gives the smallest prime base b_n to which q = (p_i, b_(n-1)) is a Wieferich prime. 0
 2, 5, 3, 7, 17, 5, 19, 131, 7, 7, 127, 659, 19, 19, 11, 911, 503, 127, 127, 3, 13, 7331, 9833, 911, 911, 17, 19, 17, 167149, 49603, 7331, 7331, 131, 127, 131, 19, 387749, 327317, 167149, 167149, 659, 911, 659, 127, 23, 17153317, 13900147, 387749, 387749, 503 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Array starts: 2    5    7   19    127    911     7331   167149    387749  17153317 ... 3   17  131  659    503   9833    49603   327317  13900147 144229223 ... 5    7   19  127    911   7331   167149   387749  17153317       ... 7   19  127  911   7331 167149   387749 17153317 432383657       ... 11   3   17  131    659    503     9833    49603    327317       ... 13  19  127  911   7331 167149   387749      ... 17 131  659  503   9833  49603   327317      ... 19 127  911 7331 167149 387749 17153317      ... 23 263   79   31    229    503      ... 29  41  313 1499    941  12011      ... ... LINKS EXAMPLE A(6,4) = 911, since the 6th prime is 13 and the smallest prime Wieferich base for 13 is 19. Applying this procedure recursively to the resulting bases a total of b-1 = 3 times leads to 911. PROG (PARI) forprime(p=1, 30, b=1; i=0; q=p; print1(p, ", "); while(i < 6, b++; if(Mod(b, q^2)^(q-1)==1 && isprime(b), print1(b, ", "); q=b; b=1; i++)); print("")) CROSSREFS Cf. A001220, A244249. Second column of table is A125636. Sequence in context: A082152 A084334 A096878 * A134563 A192178 A201914 Adjacent sequences:  A249159 A249160 A249161 * A249163 A249164 A249165 KEYWORD nonn,tabl AUTHOR Felix FrÃ¶hlich, Oct 22 2014 STATUS approved

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Last modified June 21 09:22 EDT 2021. Contains 345358 sequences. (Running on oeis4.)