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 A325883 #4 May 26 2019 15:01:04 %S A325883 1451,1482,3145,3147,3277,3365,3376,4339,4357,4365,4393,4625,5649, %T A325883 5850,7282,7624,8641,8956,8957,9149,9449,10040,10093,10538,10835, %U A325883 10889,12001,12476,12907,13253,14005,14027,14032,14500,15029,15229,15797,15857,16249,16757 %N A325883 Bases b where exactly seven primes p with p < b exist such that p is a base-b Wieferich prime. %C A325883 Numbers n such that A255920(n) = 7. %o A325883 (PARI) is(n) = my(i=0); forprime(p=1, n-1, if(Mod(n, p^2)^(p-1)==1, i++)); i==7 %Y A325883 Cf. A255920. %Y A325883 Cf. bases b with exactly k base-b Wieferich primes less than b: A255921 (k=0), A255922 (k=1), A255923 (k=2), A255924 (k=3), A255925 (k=4), A325881 (k=5), A325882 (k=6), A325884 (k=8), A325885 (k=9), A325886 (k=10). %K A325883 nonn %O A325883 1,1 %A A325883 _Felix Fröhlich_, May 26 2019